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• A bifunctional nanohybrid was facilely constructed by electrostatic interaction. • It displayed an enhanced activity for H 2 production and tetracycline removal. • The increased visible absorption and charge transfer were obtained. • The nanohybrid showed a high photocatalytic stability in the cycling test. The fabrication of the nanomaterials with high photocatalytic activity has been the focus of environmentally friendly photocatalytic technology. Herein, a special nanohybrid was synthesized from protonated carbon nitride (H-CN) and iron porphyrin metal–organic framework (FePMOF) by electrostatic self-assembly strategy. The nanohybrid was identified as a bifunctional CN-based material for both photocatalytic H 2 evolution and degradation of tetracycline (TC). The hydrogen production over the obtained H-CN/FePMOF was 7.57 times higher than that of H-CN. Moreover, it also exhibited ideal photocatalytic degradation efficiency towards TC within 20 min, which was greatly higher than some comparisons reported. The predominant performance of the H-CN/FePMOF nanohybrid can be attributed to the intimate interfacial contact, which facilitated the separation and migration of photogenerated carriers. Moreover, the light absorption was broadened upon the introduction of FePMOF. This work provides a new insight for constructing some bifunctional carbon nitride-based photocatalysts used in the fields of energy and environment. [ABSTRACT FROM AUTHOR]

• Transition-metal complexes of porphyrins have been successfully used as models of cytochrome P450 enzyme for the oxidation of organic compounds such as hydrocarbons. • An iron porphyrin (Fe(III)TCPP-OMe) is used as the catalyst for the oxidation of xanthene with peroxide oxidants. • The Fe(III)TCPP-OMe/peroxide oxidants system shows high catalytic oxidation efficiency of xanthene and high selectivity for the formation of 9-H-xanthene-9-ol. • This work provides an efficient approach for the syntheses of xanthene derivatives. Cytochrome P450 enzyme is a superfamily of heme-containing enzyme, which play an important part in the metabolism of xenobiotics and biosynthesis of natural products. Cytochrome P450 enzyme is able to catalyze a series of challenging oxidation reactions, thus, it has attracted increased attention as a promising biocatalyst for synthetic chemistry. Transition-metal complexes of porphyrins have been successfully synthesized as models for the cytochrome P450 enzyme, and used to the oxidation of organic compounds such as hydrocarbons. In the current study, an iron porphyrin, 5,10,15,20-tetra (4-methoxyphenyl) porphine ferric chloride (III) (Fe(III)TCPP-OMe) is used as the catalyst for the oxidation of xanthene with peroxide oxidants (cumyl hydroperoxide (CmOOH) and tert ‑butyl hydroperoxide (t -BuOOH)). Fe(III)TCPP-OMe shows high catalytic oxidation efficiency of xanthene and high selectivity for the formation of 9-H-xanthene-9-ol. This work provides a feasible method for the oxidation of hydrocarbons. [Display omitted] [ABSTRACT FROM AUTHOR]

Iron insertion into porphyrins is an essential step in heme biosynthesis. In the coproporphyrin-dependent pathway, specific to monoderm bacteria, this reaction is catalyzed by the monomeric enzyme coproporphyrin ferrochelatase. In addition to the mechanistic details of the metalation of the porphyrin, the identification of the substrate access channel for ferrous iron to the active site is important to fully understand this enzymatic system. In fact, whether the iron reaches the active site from the distal or the proximal porphyrin side is still under debate. In this study we have thoroughly addressed this question in Listeria monocytogenes coproporphyrin ferrochelatase by X-ray crystallography, steady-state and pre-steady-state imidazole ligand binding studies, together with a detailed spectroscopic characterization using resonance Raman and UV–vis absorption spectroscopies in solution. Analysis of the X-ray structures of coproporphyrin ferrochelatase-coproporphyrin III crystals soaked with ferrous iron shows that iron is present on both sides of the porphyrin. The kinetic and spectroscopic study of imidazole binding to coproporphyrin ferrochelatase‑iron coproporphyrin III clearly indicates the presence of two possible binding sites in this monomeric enzyme that influence each other, which is confirmed by the observed cooperativity at steady-state and a biphasic behavior in the pre-steady-state experiments. The current results are discussed in the context of the entire heme biosynthetic pathway and pave the way for future studies focusing on protein-protein interactions. Spectroscopic and kinetic experiments reveal that exogeneous imidazole ligand binds both distal and proximal coordination positions of Fe-porphyrin in active site of Listeria monocytogenes coproporphyrin ferrochelatase. X-ray crystallography confirms the presence of ferrous iron on the distal and proximal sides, as well as in the porphyrin, during in vitro metalation. [Display omitted] • Mechanistic insights on the ferrous iron entry path to coproporphyrin ferrochelatase. • X-ray structure show binding of Fe2+ to distal and proximal sides of porphyrin. • Imidazole binding confirms that both entry paths are accessible. • Distal and proximal mutations affect the imidazole binding affinity. [ABSTRACT FROM AUTHOR]

• The reaction mechanism of the CO 2 reduction to HCOO− by iron porphyrins were revealed using DFT calculations. • The calculated redox potentials are in agreement with the available experimental values. • A detailed electronic structure analysis provides important insight into the nature of key intermediates and transition states. • The formal Fe(I) complex bearing a protonated amine pendant can catalyze CO 2 reduction to HCOO − through the C-protonation of an FeII-OCO•− species. Electrocatalytic reduction of CO 2 into value-added chemicals has been considered as a promising pathway to mitigate the energy crisis and global warming. Iron porphyrins have been extensively studied for electrocatalytic CO 2 reduction reaction (CO 2 RR), known for their ability to promote CO 2 -to-CO conversion. However, the mechanism of CO 2 -to-HCOO− conversion by Fe porphyrin remains unclear. Here, by means of density functional theory (DFT) calculations, we investigated the detailed mechanism of a novel Fe porphyrin catalyst for CO 2 reduction to HCOO− in its Fe(I) state. Our results demonstrated that the reduction of CO 2 to HCOO− proceeds via the C-protonation of an FeII-OCO•− complex, rather than through the hydrolysis of an FeIII-COOH complex or CO 2 insertion in an Fe−H bond. Furthermore, the FeIII-COOH complex is found to be a unstable intermediate. Protonation of its hydroxyl group, accompanied by C−OH bond cleavage to produce CO, is both thermodynamically and kinetically unfeasible. Instead, the FeIII-COOH complex undergoes a coordination switch followed by a conformational change to form the active FeII-OCO•− complex, which promotes the production of HCOO−. Moreover, the single-electron reduction of FeIII-COOH gives FeII-COOH, leading to formation of CO rather than HCOO−. The insights gained from this study may contribute to design of electrocatalysts for selective CO 2 reduction to formate. [Display omitted] [ABSTRACT FROM AUTHOR]

Inspired by the iron porphyrin structure of natural horseradish peroxidase (HRP), an efficient carbon-based nanozyme was fabricated using nitrogen-doped graphene quantum dots (NGQDs) and iron ion (Fe3+) nanocomposite, enabling selective distinguishment of hydroquinone (HQ) from its isomers. NGQDs with good dispersibility and uniform size were synthesized via a one-step hydrothermal process. NGQDs lacked peroxidase-like activity but the formed nanocomposite (Fe3+-NGQDs) upon Fe3+ addition possessed high peroxidase-like activity. Fe3+-NGQDs nanocomposite exhibited shuttle-shaped structure (∼30 nm), the lattice structure of NGQDs and electron transfer between Fe3+ and NGQDs. The Fe3+-NGQDs nanocomposite can catalyze the production of superoxide radicals (•O 2 −) from H 2 O 2. The Michaelis constant (K m) of Fe3+-NGQDs (0.115 mM) was lower than that of natural HRP (0.434 mM) with 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate and the maximum initial reaction rate (V max , 16.47 × 10−8 M/s) was nearly 4 times higher than that of HRP using H 2 O 2 substrate. HQ, unlike its isomers catechol (CC) and resorcinol (RE), could consume •O 2 − generated from the decomposition of H 2 O 2 catalyzed by Fe3+-NGQDs nanocomposite, reducing the oxidation of TMB. This principle enabled selective colorimetric determination of HQ ranged from 1 μM to 70 μM and a limit of detection (LOD) of 0.2 μM. Successful determination of HQ in pond water was also realized. [Display omitted] • Nitrogen-doped graphene quantum dots (NGQDs) were one-step synthesized with high yield. • NGQDs formed nanocomposite (Fe3+-NGQDs) upon Fe3+ addition. • Fe3+-NGQDs nanocomposite possessed high peroxidase-like activity. • Selective colorimetric detection of hydroquinone (HQ) from its isomers using Fe3+-NGQDs nanozyme. [ABSTRACT FROM AUTHOR]

Fe-N-C materials are among the most promising platinum group metals-free catalysts for air cathode of Zn-air batteries (ZABs). However, they are still limited by sluggish reaction kinetics. Herein, we synthesize a novel and effective mesoporous carbon embedded with CoFe nanoclusters, coated with graphitic carbon layers (denoted as CoFe-FeNC). CoFe-FeNC is derived from the pyrolysis of metal-organic complex precursors with grafted iron porphyrin. The CoFe-FeNC catalyst exhibits a half-wave potential (E 1/2) of 0.876 V for the oxygen reduction reaction (ORR) and a potential of 1.526 V at 10 mA cm−2 (E j=10) for the oxygen evolution reaction (OER) in alkaline solutions. Theoretical calculations reveal that the presence of CoFe clusters regulates the electronic structure, optimizing adsorption and desorption during the catalytic reaction. Moreover, flow-ZABs utilizing CoFe-FeNC as the cathode material demonstrate a high specific capacity of 767.5 mAh g Zn −1 and an ultra-long lifespan exceeding 1200 h. Additionally, flexible quasi-solid-state rechargeable ZABs incorporating CoFe-FeNC electrocatalysts as the cathode demonstrate well cycling and mechanical flexibility. [Display omitted] • A facile method for the fabrication of mesoporous nitrogen-carbon material decorated by CoFe clusters (CoFe-FeNC). • CoFe-FeNC showed highly efficient catalytic activities for OER and ORR in alkaline media. • The bifunctional catalysts was employed in flow and flexible Zn-air battery. • Theoretical calculations claim the electronic structure and d-band center modulation between Fe-N-C and CoFe clusters. [ABSTRACT FROM AUTHOR]

The nanozyme, acting as the signal labeling reporter, is widely employed in colorimetric immunoassays due to its exceptional catalytic activity and reliable performance. Nonetheless, when immobilized on the nanozyme's surface, there is a decline in catalytic activity, which hinders its ability to meet the escalating demand for advanced colorimetric immunoassays. Herein, we introduce a novel MILL-88@TcP nanozyme, formed by encapsulating iron porphyrins (TcP) within metal-organic frameworks (MILL-88), where the catalytic activity of TcP is fully preserved through ethanol-induced release. Leveraging the superior encapsulation capacity and enzyme-mimicking characteristics of MILL-88, the MILL-88@TcP nanozyme demonstrates a remarkable colorimetric performance, 1430-fold higher than that of MILL-88 alone. Furthermore, we developed the MILL-88@TcP nanozyme-based Enzyme-Linked Immunosorbent Assay (N-ELISA) for enhanced sensitivity in detecting Salmonella typhimurium , achieving a detection limit of 1.68 × 102 CFU/mL, approximately 500-fold enhancement compared to the traditional HRP-based ELISA (8.35 × 104 CFU/mL). Notably, the average recoveries ranged from 91.50 % to 108.50 % with a variation of 3.53 %–10.41 %, indicating high accuracy and precision. Collectively, this study highlights that the MILL-88@TcP nanozyme, with its superior catalytic performance and anti-interference capabilities, holds promise as a colorimetric labeling reporter to enhance the detection efficacy of colorimetric immunoassays and has the potential to establish a more stable and sensitive colorimetric assay platform. [Display omitted] • A nanozyme with cocatalytic characteristics was synthesized by encapsulating iron porphyrin in MILL-88. • The MILL-88@TcP nanozyme demonstrated a remarkable colorimetric performance 1430 times higher than that of MILL-88. • The MILL-88@TcP nanozyme-based ELISA offered approximately a 500-fold increase in sensitivity compared to HRP-based ELISA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reaction mechanism for the reduction of CO 2 to CH 4 of copper, cobalt, and iron porphyrin metal–organic frameworks (PMOFs) studied by density functional theory. • The hydrogen evolution reaction (HER) is inhibited by all four copper PMOFs, with good selectivity for CO 2 reduction reaction (CO 2 RR), but requires higher overpotentials. • Cobalt PMOF has better HER performance than CO 2 RR. • Iron PMOF can reduce CO 2 at low overpotentials and inhibit HER, but the strong binding capacity of *CO to iron atoms poisons the catalyst at low overpotentials, and increasing the overpotential solves this drawback, but reduces selectivity. • Abstracts. • Two-dimensional porphyrin metal–organic frameworks (PMOFs) are effective catalysts for CO 2 reduction. The effects of metal paddlewheel clusters/phenyl modified CuPMOFs (M 1 O/ phenyl-CuPMOFs, M 1 = Zn, Co and Cu) and CuO-modified PMOFs of different metal centers (CuO-M 2 PMOFs, M 2 = Cu, Co and Fe) on the reduction behavior of CH 4 by CO 2 were systematically investigated by density functional theory. The results indicate that M 1 O/phenyl-CuPMOFs (M 1 = Zn, Co and Cu) need high overpotential to reduce CO 2 , yet effectively inhibit the hydrogen evolution reaction (HER). The CuO-CoPMOF preferentially produces HER and inhibits CO 2 reduction reaction process. The CuO-FePMOF exhibits an excellent CO 2 reduction ability, with a low Gibbs free energy change of 0.26 eV for the rate-determining step. Nevertheless, CuO-FePMOF can be poisoned at low voltages due to the formation of *CO. One potential solution to this disadvantage is to increase the operating voltage, although this may result in the occurrence of HER. [ABSTRACT FROM AUTHOR]

[Display omitted] • The iron porphyrins (FeTPP) derivatives are loaded on graphene to fabricate the Fe site with precise spatial arrangement. • DFT reveals that the electron-donating groups optimize the electronic configuration of Fe site. • The FeTPP modified by the electron-donating group accelerates the conversion kinetics of sulfur species. Lithium−sulfur (Li−S) batteries have become an ideal candidate for the next generation of rechargeable batteries for the high theoretical energy density. However, the sluggish redox kinetics hampered the development of Li−S batteries. It is reported that the conversion kinetics of lithium polysulfides (LiPSs) can be accelerated by introducing catalytic materials. The macrocyclic metal porphyrins have attracted extensive attention due to their excellent chemical stability and structural tunability. Herein, we designed a series of iron porphyrins substituted by the electron-donating and electron-withdrawing groups. According to electrochemical characterization and theoretical calculation, the functional group can switch the spin state of central Fe and modulate their catalytic performance. The methoxy-substituted iron porphyrin (FeTPP-4OMe) shows smaller band gap and facilitates the electron transfer. As a result, Li−S batteries with FeTPP-4OMe delivered a specific capacity of 1,062.0 mA h g−1 and retained a high specific capacity of 771.4 mA h g−1 at 0.5 C after 500 cycles with a capacity fading of 0.055 %. This work provides a guidance for the functional group modification of metal macrocyclic compounds in Li−S batteries. [ABSTRACT FROM AUTHOR]

With the energy crisis increasing, there is a growing focus on using renewable biomass to develop biomass carbon catalysts for the oxygen reduction reaction (ORR). This work presents a facile pre-etch strategy to prepare rice husk (RH)-derived self-doped Si carbon (RHSiC) with optimized Si content and porous structure. Subsequently, iron porphyrin (FeTPP) is loaded onto RHSiC to form the Fe-N-SiC catalyst, ensuring the stable integration of the iron-nitrogen coordination (Fe-N x) into RHSiC, effectively anchoring a single Fe atom. The optimal Fe-N-SiC_2 catalyst, prepared through pre-etching with 10 wt% NaOH at 30℃ for 1 hour, exhibits exceptional activity in both alkaline (E 1/2 = 0.876 V) and acidic (E 1/2 = 0.835 V) media. Furthermore, the Fe-N-SiC_2 catalyst displays an impressive power density of 106.6 mW cm−2 and outstanding durability in the constructed Zn-air battery (ZAB). Theoretical calculations confirm that doping Si atoms into carbon support significantly enhances the adsorption of O 2 molecules. Additionally, when Si atoms are located closer to the Fe-N 4 active center, it becomes more favorable for the ORR reaction to occur. [Display omitted] • A new Fe-N-SiC ORR catalyst is fabricated using iron porphyrin and rice husk carbon. • Facile NaOH etching technique is employed to control the Si content. • The Fe-N-SiC_2 catalyst shows good ORR activity in both alkaline and acidic media. • Calculations show that Si atoms in the carbon support enhance the adsorption of O 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Colorimetric, fluorometric and color-read probes were developed for H 2 O 2 and glucose detection. • Multiporphyrin arrays anchored on quartz plate provided a convenient way for tracking color in real time. • A color-read detection was achieved by using the mobile phone. • Two-dimensional arrangement of iron porphyrins enhanced catalytic efficiency and detection limit. Multi(metallo)porphyrin arrays are important artificial biomimetics for mimicking the biological catalytic reactions in nature. Here, we report construction of multi(iron)porphyrin array ultrathin films on the quartz surface by coordination-driven layer-by-layer (LBL) assembling method with the Pd(II) ion as a connector and iron(III) tetrapyridylporphyrin (FeTPyP) as a linker. It is revealed that the (Pd-FeTPyP) n LBL multilayers can catalyze oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 with peroxidase-like activity, resulting in the formation of the blue-colored oxidized TMB (oxTMB). Coupled with glucose oxidase, three sensitive probes based on the colorimetric, fluorometric and color-read methods have been developed by using modified quartz plates as the heterogenous catalyst, with a glucose detection limit of about 0.89, 1.5 and 0.65 μM, respectively. Mechanism studies confirm an enhanced affinity between (Pd-FeTPyP) n and H 2 O 2 /TMB molecules and an improved catalytic performance, which are attributed to the reason that the FeTPyP macrocycles are well-dispersed and arranged on the two-dimensional quartz surface. Furthermore, owing to chemically anchored on the transparent quartz surface, the (Pd-FeTPyP) n films exhibit good stability with naked-eye observation of color change under moderate conditions, thus providing a potential candidate for developing colorimetric, fluorometric and color-read glucose biosensors. [ABSTRACT FROM AUTHOR]

Resonance Raman (rR) spectroscopy has been applied to study the nature of the iron-oxo (Fe=O) moiety of oxoiron(IV) porphyrin π-cation radical complex (CompI). While the axial ligand effect on the nature of the Fe=O moiety has been studied with rR spectroscopy, the porphyrin ligand effect has not been studied well. Here, we investigated the porphyrin ligand effect on the Fe=O moiety with rR spectroscopy. The porphyrin ligand effect was modulated by the electron-withdrawing effect of the porphyrin substituent at the meso-position. This study shows that the frequency of the Fe=O stretching band, ν (Fe=O), hardly change even when the electron-withdrawing effect of the porphyrin substituent changes. This result is further supported by theoretical calculation of CompI. The natural atomic charge analysis reveals that the oxo and axial ligands work to buffer the electron-withdrawing effect of the porphyrin substituent. The electron-withdrawing porphyrin substituent shifts an electron population from the ferryl iron to the porphyrin, but the decreased electron population on the ferryl iron is compensated by the shift of the electron population from the oxo ligand and the axial ligand. The shift of the electron population makes the Fe–axial ligand bond length short, but the Fe=O bond length unchanged, resulting in the invariable ν (Fe=O) frequency. We investigated the electron-withdrawing effect of the porphyrin ligand on the iron-oxo (Fe=O) moiety with resonance Raman spectroscopy. This study shows that the frequency of the Fe=O stretching band hardly change even when the electron-withdrawing effect of the porphyrin substituent changes. [Display omitted] • Electron-withdrawing effect of the porphyrin ligand on the iron-oxo stretching band. • Frequency of the iron-oxo stretching band is insensitive to the porphyrin ligand effect. • The oxo and axial ligands work to buffer the porphyrin ligand effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances in the use of molecular catalysts and single-atom catalysts (SACs) for the conversion of CO 2 into C 1 molecules are reported. • The use of Mn, Ni, Fe, and Co complexes and SACs have gained prominence in the CO 2 electroreduction due to their large availability. • The comparison between SACs and molecular catalysts for CO 2 electroconversion to C 1 reveals similar performance characteristics in terms of FE. The electrochemical reduction of carbon dioxide driven by renewable energy sources represents a crucial pathway for CO 2 conversion and utilization, offering a viable approach for achieving sustainable carbon neutralization. Recent advancements in the design and comprehension of catalytic materials and electrolyte systems have steadily enhanced the performance of CO 2 electroreduction (CO 2 ERR). Among the promising materials for CO 2 electroreduction, transition metals, such as manganese, nickel, iron, and cobalt, have gained prominence due to their availability in contrast to expensive noble metals. This review delves into the more recent advances on the utilization of molecular catalysts and single-atom catalysts (SACs) for the conversion of CO 2 into carbon monoxide and other C 1 molecules. The utilization of catalysts based on organometallic molecular complexes has demonstrated notable efficiency. This approach enables the fine-tuning of the electrical and coordination characteristics of the metal center, thereby enhancing metal utilization, reducing poisoning events, and allowing for selectivity control. While much of the research has traditionally focused on homogeneous CO 2 electroreduction, recent years have seen increasing attention towards the heterogenization of molecular catalysts. The main organometallic complexes presented in this review are cobalt and iron porphyrin, cobalt phtalocyanine and manganese bipyridine, anchored on carbon-based electrodes. Moreover, single-atom catalysts have emerged as promising candidates for driving CO 2 ERR, due to their exceptional performance. Among these catalysts, the single-atom Metal-Nitrogen-Carbon (M-N-C) structure stands out as particularly promising. Additionally, the incorporation of nitrogen, sulfur, and oxygen to dope the carbon support can ensure a uniform distribution of the atomic metal within the catalyst. Here, iron, cobalt and nickel SACs are outlined, presenting diverse support materials and operating conditions. Both SACs and molecular catalysts have demonstrated commendable Faradaic efficiencies, indicating their capability to convert CO 2 into CO with a high degree of selectivity. These findings suggest that SACs, with their single-atom configurations, and molecular catalysts, with their tailored molecular structures, offer viable and comparable routes for advancing the CO 2 ERR. [ABSTRACT FROM AUTHOR]

Heme, a near ubiquitous cofactor, is synthesized by most organisms. The essential step of insertion of iron into the porphyrin macrocycle is mediated by the enzyme ferrochelatase. Several ferrochelatases have been characterized, and it has been experimentally shown that a fraction of them contain [2Fe-2S] clusters. It has been suggested that all metazoan ferrochelatases have such clusters, but among bacteria, these clusters have been most commonly identified in Actinobacteria and a few other bacteria. Despite this, the function of the [2Fe-2S] cluster remains undefined. With the large number of sequenced genomes currently available, we comprehensively assessed the distribution of putative [2Fe-2S] clusters throughout the ferrochelatase protein family. We discovered that while rare within the bacterial ferrochelatase family, this cluster is prevalent in a subset of phyla. Of note is that genomic data show that the cluster is not common in Actinobacteria, as is currently thought based on the small number of actinobacterial ferrochelatases experimentally examined. With available physiological data for each genome included, we identified a correlation between the presence of the microbial cluster and aerobic metabolism. Additionally, our analysis suggests that Firmicute ferrochelatases are the most ancient and evolutionarily preceded the Alphaproteobacterial precursor to eukaryotic mitochondria. These findings shed light on distribution and evolution of the [2Fe-2S] cluster in ferrochelatases and will aid in determining the function of the cluster in heme synthesis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ferrochelatases insert ferrous iron in porphyrins in the heme biosynthesis pathway. • The porphyrin proximal ligand is not conserved in the active site of ferrochelatases. • Proximal mutations alter the H-bonds between the porphyrin and the protein. • Effects on the activity are induced by the polarity of the mutated proximal ligand. • The weak coordination by the proximal ligand is essential for substrate and product. Ferrochelatases catalyze the insertion of ferrous iron into the porphyrin during the heme b biosynthesis pathway, which is fundamental for both prokaryotes and eukaryotes. Interestingly, in the active site of ferrochelatases, the proximal ligand coordinating the porphyrin iron of the product is not conserved, and its catalytic role is still unclear. Here we compare the L. monocytogenes bacterial coproporphyrin ferrochelatase native enzyme together with selected variants, where the proximal Tyr residue was replaced by a His (i.e. the most common ligand in heme proteins), a Met or a Phe (as in human and actinobacterial ferrochelatases, respectively), in their Fe(III), Fe(II) and Fe(II)–CO adduct forms. The study of the active site structure and the activity of the proteins in solution has been performed by UV–vis electronic absorption and resonance Raman spectroscopies, biochemical characterization, and classical MD simulations. All the mutations alter the H-bond interactions between the iron porphyrin propionate groups and the protein, and induce effects on the activity, depending on the polarity of the proximal ligand. The overall results confirm that the weak or non-existing coordination of the porphyrin iron by the proximal residue is essential for the binding of the substrate and the release of the final product. [ABSTRACT FROM AUTHOR]

• Oxidative stability of myoglobin (Mb) was investigated under magnetic field treatment. • The central iron was protected for porphyrin ring first oxidized by hydroxyl radical. • 12 mT magnetic field could slow down oxidation damage of hydroxyl radical to Mb. • Sarcoplasmic protein shielded Mb from oxidation damage caused by magnetic fields. This study aimed to investigate the effect of magnetic fields (0, 3, 6, 12 mT) on the oxidation characteristics of myoglobin (Mb) in the sarcoplasmic protein (SP) system and to understander the underlying mechanism. The metmyoglobin content, Soret band of heme iron porphyrin, protein conformation and molecular weight distribution were measured in different Mb and SP samples. The results showed that the primary oxidation site of hydroxyl radical on Mb was likely to be the porphyrin ring structure and the side chain group of protein rather than the central iron atoms, what's more, 12 mT magnetic field treatment had an inhibitory effect on the oxidative damage induced by hydroxyl radical. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis of iron-incorporated molecule-based ordered carbonaceous frameworks (OCFs) was achieved for the first time. • The carbonization behavior and the structures of obtained OCFs were well analyzed by TG-MS, PXRD, XAFS, and HAADF-STEM. • The introduction of ethynyl groups to the meta -positions of phenyl groups plays a crucial role for achieving OCFs. • The OCFs with the conserved N 4 -Fe coordination sphere enabled electrochemical reduction of CO 2 to CO. Iron-incorporated ordered carbonaceous frameworks (OCFs) have been synthesized by the pyrolysis of iron porphyrin with ethynyl groups as polymerizable/carbonizable moieties at a temperature higher than 600 °C. The pyrolysis behavior is analyzed by thermogravimetry-differential thermal analysis-mass spectrometry, and the obtained carbon materials are characterized by X-ray diffraction, X-ray absorption fine structure, and high-angle annular dark-field scanning transmission electron microscopy. The introduction of ethynyl groups at the meta positions of the peripheral phenyl groups is essential for efficient cross-linking upon thermal polymerization. The thermally stable polymer thus obtained can be transformed into OCFs with high carbonization yield of 93 % at the subsequent carbonization. OCFs possess periodic structural regularity and porphyrin Fe-N 4 coordination structure, and exhibit electrocatalysis for the conversion of CO 2 into CO. [ABSTRACT FROM AUTHOR]

Metalloporphyrins (FeTBAP, MnTBAP, FeTMPyP and MnTMPyP) have been proposed as effective therapeutic agents in ONOO−-related disease including type 2 diabetes (T2D). As these metalloporphyrins share the structural similarities of the planar aromatic conjugation with a valuable class of inhibitors against amyloids fibrillation, they might be effective inhibitors via aromatic π - π stacking interactions with amyloid peptides. Here, we found that the anionic metalloporphyrins (FeTBAP and MnTBAP) are effective inhibitors against hIAPP fibrillation, while, the cationic metalloporphyrins (FeTMPyP and MnTMPyP) only have limited inhibitory effects. Besides, the porphyrin with iron center is more effective than the one with manganese center. Our results favor the electrostatic attraction contributes the main reason to the inhibitory effect between the anionic porphyrins and hIAPP, followed by the π-π stacking interactions between aromatic ring of porphyrins and hIAPP and the stronger coordination ability of iron center to hIAPP. Additionally, by comparison with FeTBAP, which can completely inhibit cytotoxicity induced by hIAPP via stabilizing hIAPP monomers, MnTBAP fails to reverse the cytotoxicity due to that it can only delay the transition of hIAPP from α-helix to β-sheet rich oligomers. Our results provide theoretical significance for further designing or screening of metalloporphyrins as bifunctional antidiabetic drugs. [ABSTRACT FROM AUTHOR]

Cytochrome P450 55A3 (CYP55A3) is an enzyme with the catalytic activity of nitric oxide (NO) to nitrous oxide using NADH or NADPH as the electron donor. Herein CYP55A3 has been expressed in E. coli and purified by His-tag columns. The electrochemical and spectroscopic characteristic of CYP55A3 and its interaction with NO has been studied. The direct electrochemistry of Fe3+/Fe2+ redox peaks in CYP55A3 was realized on the pyrolitic graphite electrode with the redox potential of −475 mV in pH 7.0 phosphate buffer. With the addition of NO a ferric nitroxyl complex (Fe3+-NO) formed with a new reduction peak at −0.78 V. The reduction peak current increased with the concentration of NO and showed typical Michaelis-Menten kinetic characteristics with the apparent Michaelis constant Kmapp 9.78 μM. The binding constant K calculated to be 3.93 × 104 M by UV–vis method. The fluorescence emission spectra of iron porphyrin in CYP55A3 showed with the peak wavelength 633 nm, and its fluorescence intensity increased after binding with NO. The fluorescence analysis demonstrated that NADH can relay electrons to iron porphyrin and reduce NO. The reductive product of NO released and the iron porphyrin in CYP55A3 turned back to the original form. • The redox potential of CYP55A3 was measured to be −475 mV in pH 7.0 buffer. • Binding with NO a Fe3+-NO complex formed with a reduction peak at −0.78 V. • The interaction of NO and CYP55A3 resulted in a new absorption peak at 431 nm. • The binding constant K of NO and CYP55A3 was determined to be 3.93 × 104 mol/L. • Binding with NO the fluorescence intensity of iron porphyrin of CYP55A3 increased. [ABSTRACT FROM AUTHOR]

Iron is an essential nutrient for all living organisms. To acquire iron, many pathogens have developed elaborate systems to steal it from their hosts. The iron acquisition system in the opportunistic pathogen Staphylococcus aureus comprises nine proteins, called iron-regulated surface determinants (Isds). The Isd components enable S. aureus to extract heme from hemoglobin (Hb), transport it into the bacterial cytoplasm, and ultimately release iron from the porphyrin ring. IsdB and IsdH act as hemoglobin receptors and are known to actively extract heme from extracellular Hb. To limit microbial pathogenicity during infection, host organisms attempt to restrict the availability of nutrient metals at the host-pathogen interface. The human acute phase protein haptoglobin (Hp) protects the host from oxidative damage by clearing hemoglobin that has leaked from red blood cells and also restricts the availability of extracellular Hb-bound iron to invading pathogens. To investigate whether Hp serves an additional role in nutritional immunity through a direct inhibition of IsdH-mediated iron acquisition, here we measured heme extraction from the Hp-Hb complex by UV-visible spectroscopy and determined the crystal structure of the Hp-Hb-IsdH complex at 2.9 Å resolution. We found that Hp strongly inhibits IsdH-mediated heme extraction and that Hp binding prevents local unfolding of the Hb heme pocket, leaving IsdH unable to wrest the heme from Hb. Furthermore, we noted that the Hp-Hb binding appears to trap IsdH in an initial state before heme transfer. Our findings provide insights into Hp-mediated IsdH inhibition and the dynamics of IsdH-mediated heme extraction. [ABSTRACT FROM AUTHOR]

Nonradical species with great resistance to interference have shown great advantages in complex wastewater treatment. Herein, a novel system constructed by biodegradable tetrakis-(4-carboxyphenyl)-porphyrinatoiron(III) (FeIII-TCPP) and peroxymonosulfate (PMS) was proposed for facile decontamination. Nonradical pathway is observed in FeIII-TCPP/PMS, where 1O 2 and high-valent iron-oxo species play dominant roles. The genres and valence of high-valent iron-oxo species, including iron(IV)-oxo porphyrin radical-cationic species [O FeIV-TCPP•+] and iron(IV)-hydroxide species [FeIV-TCPP(OH)], are ascertained, along with their generation mechanism. The axial ligand on the iron axial site affects the ground spin state of FeIII-TCPP, further influencing the thermodynamic reaction pathway of active species. With trace catalyst in micromoles, FeIII-TCPP exhibits high efficiency by degrading bisphenol S (BPS) completely within 5 min, while Co2+/PMS can only achieve a maximum of 26.2% under identical condition. Beneficial from nonradical pathways, FeIII-TCPP/PMS demonstrates a wide pH range of 3–10 and exhibits minimal sensitivity to interference of concomitant materials. BPS is primarily eliminated through β-scission and hydroxylation. Specifically, 1O 2 electrophilically attacks the C–S bond of BPS, while high-valent iron-oxo species interacts with BPS through an oxygen-bound mechanism. This study provides novel insights into efficient activation of PMS by iron porphyrin, enabling the removal of refractory pollutants through nonradical pathway. [Display omitted] • FeIII-TCPP is an effective activator for PMS over a wide pH range of 3–10. • A wide variety of organics can be eliminated by FeIII-TCPP/PMS. • FeIII-TCPP/PMS can degrade BPS with strong resistance against water constituents. • FeIII-TCPP/PMS undergoes a nonradical pathway with FeIV(O) and 1O 2 as ROS. [ABSTRACT FROM AUTHOR]

• Nonbonding electrostatic effects on the CO 2 -to-CO reduction by iron porphyrins were revealed by means of DFT calculations. • The kinetic and thermodynamic of individual chemical steps in the reaction cycle were systematically studied. • Detailed electronic structure analysis provides important insight into the nature of key intermeidates and transition states. • The activity trend could be rationalized by the brønsted-evans-polanyi principle. • The electrostatic repulsive between the negatively charged hanging group and negatively charged CO 2 moiety plays crutical role in the rate-dermining CO 2 binding step. Iron porphyrin (Por) complexes were found to be highly efficient molecular catalysts for electrocatalytic CO 2 reduction and the catalytic performance can be modulated by the modification of ligands. Herein, density functional theory calculations were employed to investigate how the presence of second-sphere anionic carboxylate groups influences the CO 2 -to-CO conversion by Fe porphyrins. The kinetics and thermodynamics of individual chemical steps in the reaction cycle were systematically studied. Computations indicated that the catalytic active species is the ferrous complex with the two extra electrons being stored in the π system of porphyrin and the rate-determining step is the CO 2 binding. The synchronization of the Fe-to-CO 2 and ligand-to-Fe electron transfers leads to the formation of FeIII(CO 2 2−)(Por•−). The experimentally observed activity trend could be rationalized by the Brønsted-Evans-Polanyi principle. The electrostatic repulsive between the negatively charged hanging group and the CO 2 moiety destabilizes the CO 2 adduct and thereby raises the binding energy. Then, the two-step protonation occurs easily to give Fe(II)-CO. The further one-electron reduction triggers the dissociation of CO to regenerate of the formal Fe(I) porphyrin catalyst. The insights gained from this study may be helpful in designing efficient electrocatalysts for CO 2 reduction. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile approach was utilized to construct biomimetic COFs nanozymes. • The doped histidine boosted the catalytic capacity of Fe-COF-H3. • Urate oxidase was immobilized in Fe-COF-H3 to construct enzyme-nanozyme cascade system. • The UOx@Fe-COF-H3 was applied for the detection of uric acid in biological samples. Imitating catalytic sites of natural enzymes is a promising approach to accurately improve the catalytic performances of nanozymes. Herein, inspired by the structure of natural horseradish peroxidase (HRP), three-component condensation strategy is unitized to design histidine (His) functionalized iron porphyrin covalent organic frameworks (Fe-COF-H3) nanozyme with peroxidase-like (POD-like) activity. The introduced His could form favorable microenvironment around the iron porphyrin structure, enhancing the catalytic capacity of COF nanozyme. Taking advantage of its excellent POD-like activity, Fe-COF-H3 was utilized as a carrier to immobilize urate oxidase (UOx) for the construction of enzyme-nanozyme cascade system (UOx@Fe-COF-H3). The UOx@Fe-COF-H3 was successfully applied for the colorimetric detection of uric acid (UA) in biological samples. This work not only offers a new insight to develop high-efficiency COF nanozymes, but also expands the application of COF nanozyme for the construction of enzyme-nanozyme cascade system. [ABSTRACT FROM AUTHOR]

Inspired by natural hemin structure, the fabrication of metal organic framework (MOF) nanomaterials constructed by metal ions and iron porphyrin for peroxidase mimicking has attracted extensive attention recently due to their high concentration of active sites and great channeling for substrate diffusion. Herein, by using benzoic acid as capping agent, we fabricated uniform PCN-224 nanoparticles (NPs), which were composed of Zr 6 cluster and tetrakis(4-carboxyphenyl)porphyrin (H 2 TCPP). Then Fe(Ⅲ) ions were incorporated into the center of H 2 TCPP producing iron porphyrin unit similar to hemin serving as catalytic active site. The procedure of iron incorporation didn't change the size and morphology of PCN-224 NPs. The newly formed Fe@PCN-224 NPs possessed peroxidase-like activity with much lower K m values and higher K cat values than most of peroxidase-like nanozymes as well as natural horseradish peroxidase (HRP), indicating their enhanced catalytic activity. Taking advantage of the excellent peroxidase-like activity of Fe@PCN-224 NPs, we successfully developed a colorimetric method for simple and sensitive detection of hydrogen peroxide and glucose in combination with glucose oxidase. [ABSTRACT FROM AUTHOR]

Iron porphyrins with cyano or aldehyde group in periphery are designed to produce FeC nanohybrids with exclusive metallic Fe/Fe3C or oxidative Fe3O4 nanoparticles inside. Systematic experiments and theoretical analysis discover that metallic Fe promote while oxidative Fe impede ORR process on Fe-Nx sites, leading to significantly different ORR activity. • A new strategy was developed by using the substituent-engineered iron porphyrin to produce Fe-N-C nanohybrids. • Fe-N-C electrocatalysts with metallic Fe/Fe 3 C or oxidative Fe 3 O 4 nanoparticles were developed. • Fe-N x sites exist in both catalysts and dominate ORR activity. • Metallic Fe/Fe 3 C nanoparticles promote ORR on Fe-N x sites, while oxidative Fe 3 O 4 nanoparticles slow down ORR on Fe-N x sites. • Fe(0)@FeNC exhibits superior ORR activity in half-cell test as well as Zinc-air battery. Fe-N-C materials with Fe-N x coordination sites are promising to replace the state-of-the-art Pt-based electrocatalysts for oxygen reduction reaction (ORR) due to high activity and low cost although there is still debate on its activity origin. Herein, we develop a strategy to investigate the role of iron species in Fe-N-C nanohybrids for catalysing ORR by delicately tuning the iron chemical state. By engineering peripheral substituents of iron porphyrin precursors, two Fe-N-C nanohybrids with metallic or oxidized iron species inside are achieved while holding the similar catalyst structure. Systematic experiments and theoretical analysis discover that metallic iron species promote the electrocatalytic activity of Fe-N x sites for ORR, while oxidative ones inhibit O 2 adsorption on Fe-N x sites, decreasing their ORR activity. This finding sheds light on unravelling the activity origin in Fe-N-C electrocatalysts for ORR towards their applications in energy devices. [ABSTRACT FROM AUTHOR]

• An effective oxidation of DTBP was achieved. • Highest TON and TOF values were obtained by porphyrin catalysts. • The TON and TOF values were 4300 and 8600 (h−1), respectively. • Complete conversion of DTBP was achieved in 30 min. • Ecotoxicity tests indicated less toxic reaction mixture. In this study, two water-soluble iron porphyrins bearing sulfonate and carboxylate functionalities (FePTS and FePTC, respectively) and their supported analogues were used as catalysts for the oxidation of 2,6-di- tert -butylphenol (DTBP) in a water-methanol mixture. tert -Butyl hydroperoxide (TBHP) was the oxidant and the volume ratio of water to methanol in the mixture was 1–8. The major products of the DTBP oxidation were 3,3ʹ,5,5ʹ-tetra- tert -butyl-4,4ʹ-diphenoquinone (DPQ) and 4,4′-dihydroxy-3,3′,5,5′-tetra- tert - butylbiphenyl (H 2 DPQ). Also 2,6-di- tert -butyl-1,4-benzoquinone (BQ) was the minor product of the oxidation. The results showed that FePTC was more catalytically active than FePTS in the oxidation and gave the highest TON and TOF values in comparison to those for metalloporphyrin and metallophthalocyanine based catalysts in the DTBP oxidation given in the literature. In addition, the ecotoxicity tests of the DTBP oxidation mixtures before and after oxidative catalytic treatment toward Artemia salina were performed. It was found that the toxicity of the catalytically treated DTBP mixture containing residual DTBP and products was lower than the catalytically untreated DTBP mixture. [ABSTRACT FROM AUTHOR]

The study of non-precious metal catalysts (NPMCs) as alternatives to platinum for oxygen reduction is crucial if the use of fuel cells is to become more widespread. Among NPMCs, pyrolyzed catalysts (Fe-N-C) are particularly promising in both basic and acid media. The characterization of active sites and the understanding of the oxygen reduction reaction (ORR) mechanism are crucial for the design of active Fe-N-C catalysts. In this study, we have tested the involvement of the metal centre in the ORR process at pH 13 for two pyrolyzed iron porphyrins. The pyrolyzed catalysts present a FeN4 active site structure similar to that of the porphyrin precursors. Regarding the mechanism, we have found evidence for the crucial role of the Fe(II) centres. There is a direct relation between the Fe(III)/(II) redox transition of the catalysts and the onset potential of the ORR, showing that the electrogeneration of Fe(II) from Fe(III)OH– controls the catalysis. The poisoning of iron centres with CN− induces a decrease in the ORR activity. However, the onset potential for H 2 O 2 generation remains unchanged. The Tafel plots show two different slopes at high and low overpotentials. Based on these results, we propose two different mechanisms, both dependent on the redox potential of the catalysts and the Fe O 2 binding energy. Unlabelled Image • Fe-N-C catalysts show a connection between the redox potential, Fe(III)/(II), with the onset potential of the ORR at pH 13. • Two Tafel slopes are found, the changes in slopes take place close to the redox potential of the catalysts. • The residual H 2 O 2 production is due to the nitrogen and oxidized groups present in the carbon matrix. • Two mechanisms are proposed, both dependent on the redox potential of the catalysts and the Fe(II)-O 2 binding energy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Comprehensive survey of bio-mimetic modelling of heme enzymes. • Elucidation of the role of axial ligands and distal super-structure: synthetic modifications. • Development of CcO and NOR active site models. Abstract Heme proteins catalyse a diverse set of vital life processes using very similar heme cofactor. Thus, the inorganic chemistry community has been investigating factors in the protein active site that control their reactivity. These required synthesis of artificial iron porphyrins where its axial ligand and distal environment were systematically modified. Investigation of the differences in electronic structure and reactivity of these complexes and the intermediates involved in these reactions have revealed striking differences that lead to the diverse reactivity from, apparently, similar looking active site. This review summarises some of these activities in the area of oxygen and nitric oxide activation spanning several decades of dedicated research. [ABSTRACT FROM AUTHOR]

Abstract A concise synthesis of the 2,4-dimethyldeuteroporphyrin regiospecifically labeled with 13C at the α- meso site was developed. The starting material of ethyl 3,4,5-trimethylpyrrole-2-carboxylate was first converted to a 13C-labeled 5,5′-dimethyldipyrromethene with 13C formic acid, and the resulting dipyrromethene was coupled with 5,5′-dibromodipyrromethene to afford the 13C-labeled porphyrin in 26% yield. The paramagnetic 13C NMR measurements of myoglobin with the inversion-recovery method allowed us to detect selectively the α- meso -carbon signal of the iron complex. The heme is symmetric about the α,γ- meso carbon axis to prevent the orientational disorder in protein pocket. These results indicate that the 13C-enriched 2,4-dimethyldeuteroporphyrin is a new promising tool to elucidate the structure-function relationship of many hemoproteins. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract The one-electron reduction of many molecules becomes much more favorable if combined with proton transfers or strong hydrogen bonding. Protic room temperature ionic liquids (RTILs), which can form nanodomains in solutions with molecular solvents (MS), can provide an efficient avenue for this process. In this work, we report on the voltammetry, UV/visible and resonance Raman spectroelectrochemistry of Fe(TPP)(NO) in the presence of aprotic/protic ammonium-based ionic liquids. While aprotic RTILs did shift the reduction to more positive potentials, similar shifts could be observed at much lower concentrations of diethylmethylammonium triflate (HAmOTf, a protic ionic liquid). Deconvolution of the rotating ring-disk electrode (RRDE) voltammetry revealed the partitioning of the reduced species into the ionic liquid nanodomains at low concentrations. The potential shift was substantially in excess of the value expected based on the pK a of the weak acid. Upon the addition of small amounts of the protic RTIL, the electrochemically or chemically generated anion, Fe(TPP)(NO)-, reacted rapidly with the HAm+ acid, forming a Fe(TPP)(HNO) complex. Further reduction to Fe(TPP)(NH 2 OH) could be observed on the spectroelectrochemical time scale. The outcome of this work revealed the advantageous role of protic RTIL nanodomains in accelerating the proton-coupled reductions to form more energetically favorable product. Graphical abstract Image 1 Highlights • The protonation of Fe(TPP)(NO)- in nanodomains of a protic room temperature ionic liquid (RTIL) nanodomains. • Use of rotating ring disk electrode voltammetry to elucidate reaction mechanism. • Influence of nanodomains on the kinetics of the reduction and protonation reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorinated Iron Porphyrin (FeFPor) electrocatalyst was successfully prepared. • Immobilized FeFPor on carbon cloth gave a high selectivity for CO in a wide potential range. • NaHCO 3 was the best bicarbonate catalytic medium. • Highest conversion efficiency OF CO production reached 97% at −0.49 V vs. RHE. The electrochemical CO 2 reduction reaction to form valued by-products is a challenging and a sustainable process. In general, CO 2 reduction to carbon neutral fuels requires selective and well-designed catalysts. Herein, we report perfluorinated iron porphyrin (FeFPor) for CO 2 -to-CO electroreduction in different bicarbonate electrolytes, byproducts distribution in lithium, sodium, potassium and cesium were analyzed. The immobilized FeFPor on the carbon microporous layer of the carbon cloth exhibited a high selectivity for carbon monoxide production over a wide range of potentials from −0.5 to −1 V vs. RHE in all bicarbonate solution with the NaHCO 3 being the best catalytic medium. The highest conversion efficiency to CO production reached 97% at −0.5 V vs. RHE in 0.5 M NaHCO 3 in near neutral aqueous solution (pH = 7.2). The CO electrosynthesis dropped when using lithium, potassium and cesium bicarbonates, which was due to the CO 2 concentration and reactions at the inner electrode-solution reactions. [ABSTRACT FROM AUTHOR]

Heme proteins perform diverse biochemical functions using a single iron porphyrin cofactor. This versatility makes them attractive platforms for the development of new functional proteins. While directed evolution and metal substitution have expanded the properties, reactivity, and applications of heme proteins, the incorporation of porphyrin analogs remains an underexplored approach. This review discusses the replacement of heme with non-porphyrin cofactors, such as porphycene, corrole, tetradehydrocorrin, phthalocyanine, and salophen, and the attendant properties of these conjugates. While structurally similar, each ligand exhibits distinct optical and redox properties, as well as unique chemical reactivity. These hybrids serve as model systems to elucidate the effects of the protein environment on the electronic structure, redox potentials, optical properties, or other features of the porphyrin analog. Protein encapsulation can confer distinct chemical reactivity or selectivity of artificial metalloenzymes that cannot be achieved with the small molecule catalyst alone. Additionally, these conjugates can interfere with heme acquisition and uptake in pathogenic bacteria, providing an inroad to innovative antibiotic strategies. Together, these examples illustrate the diverse functionality that can be achieved by cofactor substitution. The further expansion of this approach will access unexplored chemical space, enabling the development of superior catalysts and the creation of heme proteins with emergent properties. Adapted with permission from Ref. [ 61 ]. Copyright 2022, Royal Society of Chemistry. Synopsis Heme proteins are an attractive platform to develop designer proteins with novel functions. One way to achieve this is by replacing the native iron porphyrin with a heme analog. These conjugates serve as model systems, artificial metalloenzymes, and novel antibiotics. [Display omitted] • Heme proteins are convenient platforms to develop new functional proteins • Substituting the porphyrin cofactor with synthetic analogs enables novel properties • These conjugates serve as model systems, artificial metalloenzymes, and antibiotics • The protein matrix confers properties that are distinct from the free cofactor [ABSTRACT FROM AUTHOR]

Iron(IV)-oxo porphyrins [Fe IV (Por)O] (Por = poprhyrin), commonly called compound II models, were produced in three electron-deficient ligands by visible light irradiation of highly photo-labile porphyrin-iron(III) bromates or chlorates. The kinetics of oxygen transfer atom (OAT) reactions with aryl sulfides by these photo-generated [Fe IV (Por)O] ( 3 ) were studied in CH 3 CN solutions. The iron(IV)-oxo porphyrins under study include 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin-iron(IV)-oxo ( 3a ), 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin-iron(IV)-oxo ( 3b ), and 5,10,15,20-tetra(pentafluorophenyl)porphyrin-iron(IV)-oxo ( 3c ). As expected, complexes 3 were competent oxidants and reacted rapidly with thioanisoles to give the corresponding sulfoxides with minor over-oxidation sulfones. Apparent second-order rate constants determined under pseudo-first-order conditions for sulfide oxidation reactions are (9.8 ± 0.1) × 10 2 –(3.7 ± 0.3) × 10 1  M −1  s −1 , which are 3 to 4 orders of magnitude greater in comparison to those of alkene epoxidations and activated C H bond oxidations by the same oxo species. Conventional Hammett analyses gave non-linear correlations, indicating no significant charge developed at the sulfur during the oxidation process. For a given substrate, the reactivity order for the iron(IV)-oxo species was 3c  <  3b  <  3a , which is inverted from expectations on the basis of the electron-withdrawing capacity of the porphyrin macrocycles. The absolute rate constants from kinetic studies provided insights into the transient oxidants in catalytic reactions under turnover conditions where actual reactive intermediates are not observable. Our kinetic and catalytic competition results strongly suggest that 3 may undergo a disproportionation reaction to form a higher oxidized iron(IV)-oxo porphyrin radical cations as the true oxidant. [ABSTRACT FROM AUTHOR]

A series of unsupported and supported iron-based metalloporphyrin catalysts were prepared, possessing unique physicochemical properties and excellent catalytic activity for the transformation of biomass derived furfural to maleic acid. [Display omitted] • Metalloporphyrin type catalysts were employed in oxidation of furfural to MAD for the first time. • FeT(p-Br)PPCl catalysts was successfully immobilized on three different mesoporous materials. • The supported metalloporphyrins exhibited better catalytic performance than unsupported porphyrin catalysts. A series of porphyrin type catalysts with the metal active sites of Fe were prepared and investigated in aerobic oxidation of biomass-based furfural to maleic acid (MAD) in aqueous phase. The catalytic performance of meso -tetrakis(4-bromophenyl)porphyrin iron (III) chloride (FeT(p -Br)PPCl) immobilized on different supports was evaluated. It was interesting to find that the catalytic activity varied with the supports and followed the trend: FeT(p -Br)PPCl/SBA–15 > FeT(p -Br)PPCl/meso-ZSM–5 > FeT(p -Br)PPCl/MCM-41. The effect of reaction conditions were discussed in detail over FeT(p -Br)PPCl/SBA-15 catalyst, and 56.1% yield and 73.8% selectivity of MAD were obtained from renewable furfural under the optimal conditions. Moreover, the FeT(p -Br)PPCl/SBA-15 catalyst could be reused five times without a significant decrease of activity in recycling examinations. [ABSTRACT FROM AUTHOR]

Here, we for the first time used a thiolated amino-ligand modified multi-branched gold nanoflower as skeleton to encapsulate iron porphyrins (AuNF@FeTPPCl) as alternatives to horseradish peroxidase (HRP). After the FeTPPCl encapsulation, the HRP mimicking activity of FeTPPCl was effectively blocked by the steric hindrance of the hydrophobic layer on the AuNF surface. Upon the addition of ethanol, the loaded FeTPPCl was released into the solution in its free format and exposed the catalytic sites, resulting in the recovery of catalytic activity. The proposed encapsulation method effectively avoided the loss of catalytic activity that originated from the blocking of the catalytic active sites during immobilization. Additionally, the resultant AuNF@FeTPPCl nanocomposite exhibited a high loading level with 2.4 × 10 6 FeTPPCl molecules per AuNF, and showed considerably high catalytic activity for hydrogen peroxide and 3, 3′ 5, 5′-tetramethylbenzidine, which is approximately 40- and 172-folds higher than native HRP. Through using the as-prepared AuNF@FeTPPCl as an alternative of HRP for trace labeling, we successfully developed colorimetric immunosensors for fumonisin B 1 (FB 1 ) and hepatitis B surface antigen (HBsAg) with competitive and sandwich-type formats, respectively. The developed AuNF@FeTPPCl-based colorimetric immunosensor exhibited higher detection sensitivity for FB 1 and HBsAg than the corresponding HRP-based immunosensors. Thus, the proposed AuNF@FeTPPCl can be used as HRP mimicking analogs for developing highly sensitive colorimetric immunosensor and for loading other hydrophobic iron porphyrins or catalysts. [ABSTRACT FROM AUTHOR]

Degradation of 2,4,6-trichloropenol (TCP) with peroxymonosulfate (PMS) catalyzed by iron porphyrin tetrasulfonate ([FePTS)] was investigated in an 8-to-1 (v/v) CH 3 OH-H 2 O mixture. Typical reaction medium contained a 4.00 mL methanol solution of TCP (0.100 mmol), a 0.50 mL aqueous solution of catalyst (5.0 × 10 −4 mmol), and 0.100 mmol PMS (as 0.031 g of Oxone). The reaction was performed at ambient temperature. The conversion of TCP was 74% in 30 min and 80% in 6 h when the catalyst was [FePTS]. Amberlite IRA -900 supported [FePTS] catalyst was also prepared. In the recycling experiments the homogeneous [FePTS] lost its activity after the first cycle, while [FePTS]-Amberlite IRA 900 maintained its activity for the first 2 cycles. After the second cycle, the conversion of TCP dropped to <10% for Amberlite IRA -900 supported [FePTS] catalyst. The degradation of TCP with PMS was also attempted using cobalt, copper, nickel and palladium porphyrin tetrasulfonate catalysts, however, no catalytic activity was observed with these structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • An up-to-date introduction of porphyrin catalysts employed in CO2ERR was summarized. • The underlying kinetic and thermodynamic study of porphyrin catalysts was elaborated. • The employment of porphyrin catalysts and the associated contributing factors in homogeneous conditions are reviewed. • The techniques for immobilization of porphyrin catalysts were categorized with the specific benefits and weaknesses fully discussed. The reduction of greenhouse gas carbon dioxide (CO 2) to carbon-based fuels provides a potential solution to the sustainable and scalable energy storage challenges. To solve the issues with activity, selectivity and stability, much attention has been put on porphyrin catalysts, and more recently, the integration of porphyrins on conductive supports that operate in heterogeneous conditions. This review summarizes the main principles and strategies explored for the application of porphyrin catalysts to electrochemical CO 2 reduction, ranging from homogeneous catalysis and heterogeneous catalysis to structure modification and immobilization techniques. The first section discusses mechanistic study of porphyrin catalysts including the catalytic steps involved in CO 2 reduction, the effects of porphyrin ligands on catalytic activities. The second section provides insight into the kinetic study of porphyrin catalysts. The third section presents examples of porphyrins in homogeneous catalysis with particular focus on iron porphyrins and the boosting effects brought by Lewis acid and Brønsted acid. The next section summarizes the main techniques for the heterogenization of porphyrin catalysts on conductive supports, including non-covalent, covalent and periodic immobilization, whereas periodic immobilization comprises porphyrin scaffolds or frameworks in the structure. The last section gives an update of porphyrins employed in a flow cell. This review surveys the recent advances and basic principles of porphyrins in CO 2 reduction, and the findings can be instrumental for designing efficient and selective catalysts for CO 2 reduction. [ABSTRACT FROM AUTHOR]

It is of great significance to investigate aqueous CO 2 reduction on catalysts with redox-noninnocent ligands as they effectively facilitate CO 2 reduction but circumvent the H 2 evolution. By developing the methodology of rapid-scan FT-IR in external reflection mode, the pathway of CO 2 reduction on iron porphyrin was in-situ monitored. It's uncovered that coupled with first-electron reduction of [FeIITAPP]0, the porphyrin nitrogen is protonated as the observation of NH+ ammonium band in IR spectra, which avoids the formation of Fe–H structure for proton reduction. Moreover, an inverse kinetic isotope effect (KIE = 0.59) in formation of *COOH indicates the protonated porphyrin-N would also act as a proton relay for the efficient inner-sphere proton transfer to the activated CO 2 molecules. This work experimentally identified the proton migration pathway via the reduced porphyrin ligand as proton shuttle for the first time and should benefit the design of the catalyst of high CO 2 reduction selectivity. [Display omitted] • Redox-noninnocent ligands effectively facilitate muti-electron/proton process. • External reflection IR spectroscopy methodology provide precise spectral kinetics. • The protonated porphyrin-N avoid the formation of Fe-H structure. • The protonated porphyrin-N also act as a proton relay for efficient proton transfer. [ABSTRACT FROM AUTHOR]

In this work a polymer monolithic column was fabricated within the confines of a stainless steel column (50 × 4.6 mm i.d.) via radical polymerization by using iron porphyrin and butyl methacrylate as co-monomers, ethylene glycol dimethacrylate as crosslinking agent, ethylene glycol, isopropyl alcohol and N, N-dimethylformamide as tri-porogens, benzoyl peroxide and N , N -dimethylaniline as initiators. The resulting monolithic column was characterized by elemental analysis, scanning electron microscopy, nitrogen adsorption BET surface area, and mercury intrusion porosimetry, respectively. Results showed that the homemade monolith occupied relatively uniform pore structure, low back pressure, and enhanced selectivity for proteins in complex bio-samples. The present work described a simple and efficient method for “fractionation separation” of human plasma proteins, and it is a promising separation method for complex bio-samples in proteomic research. [ABSTRACT FROM AUTHOR]

In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe 3 O 4 @GO). Firstly, CS@Fe 3 O 4 @GO was prepared. CS@Fe 3 O 4 @GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe 3 O 4 . GO, Fe 3 O 4 and CS@Fe 3 O 4 @GO were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). Then, thrombin aptamer (T-Apt) and hemin (HM, an iron porphyrin) were sequentially modified on the surface of CS@Fe 3 O 4 @GO to form CS@Fe 3 O 4 @GO@T-Apt@HM. The immobilization properties of CS@Fe 3 O 4 @GO to T-Apt and adsorption properties of CS@Fe 3 O 4 @GO@T-Apt to HM were sequentially researched through the curves of kinetics and the curves of thermodynamics. When thrombin existed in solutions, HM was desorbed from the surface of CS@Fe 3 O 4 @GO@T-Apt@HM owing to the strong specific recognition ability between thrombin and T-Apt, causing the changes of CL signal. Under optimized CL conditions, thrombin could be measured with the linear concentration range of 5.0×10 –15 –2.5×10 −10 mol/L. The detection limit was 1.5×10 –15 mol/L (3δ) while the relative standard deviation (RSD) was 3.2%. Finally, the CS@Fe 3 O 4 @GO@T-Apt@HM-CL aptasensor was used for the determination of thrombin in practical serum samples and recoveries ranged from 95% to 103%. Those satisfactory results revealed potential application of the CS@Fe 3 O 4 @GO@T-Apt@HM-CL aptasensor for thrombin detection in monitoring and diagnosis of human blood diseases. [ABSTRACT FROM AUTHOR]

Structure-function relationships of complexes between heme and G-quadruplex DNAs have attracted interest from researchers in related fields. A carbon monoxide adduct of a complex between heme and a parallel G-quadruplex DNA formed from hexanucleotide d(TTGAGG) (heme-[d(TTGAGG)] 4 complex) has been characterized using 1 H NMR spectroscopy, and the obtained results were compared with those for the heme-[d(TTAGGG)] 4 complex previously studied in order to elucidate the effect of the incorporation of an A-quartet into stacked G-quartets in the 3′-terminal region of the DNA on the structure of the heme-DNA complex. We found that a π-π stacking interaction between the porphyrin moiety of the heme and the 3′-terminal G-quartet of the DNA is affected by the nature of the stacked G-quartets. This finding provides novel insights as to the design of the molecular architecture of a heme-DNA complex. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio. [ABSTRACT FROM AUTHOR]

This study investigates how ligands modulate metalloporphyrin activity with the goal of producing a practical biomimetic catalyst for use in the chemical industry. We immobilized iron porphyrinate [iron-tetrakis-(4-sulfonatophenyl)-porphyrin; Fe(III) (TPPS)] on powdered chitosan (pd-CTS) to form an immobilized catalyst Fe(III) (TPPS)/pd-CTS, which was characterized using modern spectroscopic techniques and used for catalytic oxidation of cyclohexane with O 2 . Amino coordination to iron porphyrin in Fe(III) (TPPS)/pd-CTS altered the electron cloud density around the iron cation, probably by reducing the activation energy of Fe(III) (TPPS) and raising the reactivity of the iron ion catalytic center, thereby improving the catalytic efficiency. One milligram of Fe(III) (TPPS) catalyst can be reused three times for the oxidation reaction to yield an average of 22.9 mol% of cyclohexanone and cyclohexanol. [ABSTRACT FROM AUTHOR]

Reduction of CO 2 is a fruitful approach for storage of renewable electric energy as well as for the production of value added chemicals. Using variously substituted iron tetraphenylporphyrins and iron and cobalt macrocyclic pentadendate N5 complexes electrochemically or photochemically reduced to their active states, selective and efficient molecular catalysis of the CO 2 -to-CO and of the CO 2 -to-HCOOH conversion was achieved at low overpotential. From fruitful joint experimental and mechanistic studies rooted in the analysis of cyclic voltammograms, the mechanisms for catalysis were fully deciphered, allowing not only to give a complete picture of the catalytic processes but also to identify the main parameters for optimizing the catalyst structure. Efficient CO 2 catalysis was performed not only in aprotic but also in aqueous conditions, opening the way to the design of electrochemical or photo-electrochemical cells, a key step for future applied devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of MOF-5-derived nitrogen-doped porous carbon by vapour phase deposition. • Fe 3 C/Fe synergizes with the active site Fe-N x to improve catalyst activity. • The current Fe N C catalyst exhibits better oxygen reduction reaction performance than Pt/C. • The current Fe N C based ZABs exhibits high specific capacity and power density. The development of non-precious metal catalysts (NPMC) for oxygen reduction reactions (ORR) is a hot topic for fuel cells and zinc-air batteries (ZABs). This study reports a method to obtain efficient Fe N C ORR catalysts via doping dicyandiamide and iron porphyrins on the pyrolyzed MOF-5 and followed pyrolysis to achieve the anchoring of Fe-N x active sites onto square-shaped structure carbon material. The prepared Fe N C catalysts exhibit excellent ORR performance under an alkaline environment with half-wave potentials up to 0.903 V, which is 57 mV higher than that of Pt/C under the same conditions. It has excellent stability and methanol resistance. Moreover, this catalyst exhibited high specific capacity (821.8 mAh g−1) and power density (111.7 mW cm−2) in assembled ZAB, and excellent charging and discharging stability. [ABSTRACT FROM AUTHOR]

Antimicrobial blue light (aBL) kills a variety of bacteria, including Porphyromonas gingivalis. However, little is known about the transcriptomic response of P. gingivalis to aBL therapy. This study was designed to evaluate the selective cytotoxicity of aBL against P. gingivalis over human cells and to further investigate the genetic response of P. gingivalis to aBL at the transcriptome level. Colony forming unit (CFU) testing, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) were used to investigate the antimicrobial effectiveness of blue light against P. gingivalis. The temperatures of the irradiated targets were measured to prevent overheating. Multiple fluorescent probes were used to quantify reactive oxygen species (ROS) generation after blue-light irradiation. RNA sequencing (RNA-seq) was used to investigate the changes in global gene expression. Following the screening of target genes, real-time quantitative polymerase chain reaction (RT-qPCR) was performed to confirm the regulation of gene expression. A 405 nm aBL at 100 mW/cm2 significantly killed P. gingivalis within 5 min while sparing human gingival fibroblasts (HGFs). No obvious temperature changes were detected in the irradiated surface under our experimental conditions. RNA-seq showed that the transcription of multiple genes was regulated, and RT-qPCR revealed that the expression levels of the genes RgpA and RgpB , which may promote heme uptake, as well as the genes Ftn and FetB , which are related to iron homeostasis, were significantly upregulated. The expression levels of the FeoB-2 and HmuR genes , which are related to hydroxyl radical scavenging, were significantly downregulated. aBL strengthens the heme uptake and iron export gene pathways while reducing the ROS scavenging pathways in P. gingivalis , thus improving the accumulation of endogenous photosensitizers and enhancing oxidative damage to P. gingivalis. • Blue light selectively kills Porphyromonas gingivalis over the human gingival fibroblasts. • Blue light increases hydroxyl radical generation by nearly 400%. • Blue light upregulates gene transcription involved in heme and iron homeostasis. • Blue light downregulates gene transcription involved in hydroxyl radical scavenging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The N -rich COFp-Fepor NH2-BPA containing abundant iron porphyrin ring was synthesized. • A sensitive NSE immunosandwich sensor was constructed based on dual signal amplification via COFs. • Primary amplification of signal was performed using long-range ordered COFp-Fepor NH2-BPA. • The secondary amplification of signal was achieved by using COFp-Fepor NH2-BPA to catalyze O2 reduction. • The constructed sensor for detecting NSE was excellent. It is very urgent to construct an efficient neuron-specific enolase (NSE) immunosensor for the early diagnosis of small cell lung cancer (SCLC). Here, a sensitive NSE immunosandwich sensor was constructed based on dual signal amplification strategy via electrocatalytic oxygen reduction by iron-porphyrin covalent organic framework (COF p -Fepor NH2-BPA). The N -rich COF p -Fepor NH2-BPA containing abundant iron porphyrin ring was synthesized and connected to gold nanoparticles (AuNPs) via Au-N bond, and further successfully bound to Ab2 via Au-S bond to form beacon probe complex of COF p -Fepor NH2-BPA/AuNPs/Ab2. Another kind of COFDva-TAB with abundant vinyl was used to bond Ab1 for forming Ab1/COFDva-TAB/GCE by thiol-ene "click" reaction. The highlight of this NSE immunosensor is that COF p -Fepor NH2-BPA is a long-range ordered material enriched of iron porphyrin units owning obvious electrochemical signal. In the O2-saturated environment, the electrochemical signal is further amplified due to the electrocatalytic reduction of O2 by iron porphyrin units. Thus, the NSE immunosensor shows a wide detection range of 500 fg/mL–100 ng/mL, a low detection limit of 166.7 fg/mL and a high sensitivity of 8.82 j/lg(cNSE/ng mL−1). This work also provides effective dual signal amplification strategy for electrochemical immunoassay based on COFs. [ABSTRACT FROM AUTHOR]

• Non-catalytic demetallization process successfully removed 89.2 % metals in sewage sludge biocrude. • Iron porphyrins in cyanobacteria (generally referred as Spirulina algae) biocrude makes demetallization process ineffective. • High organic loss (20.1%) is attributed towards basic nitrogenates and oxygenates with low carbon number. • By utilizing FTICR MS, the complex interplay between acids and organic contaminants (organometallics, nitrogen, and oxygen) was explored in detail. Higher metallic content in nitrogen-rich hydrothermal liquefaction (HTL) biocrudes is a bottleneck during downstream hydroprocessing, which is necessary for producing drop-in biofuels from urban residues and algal feedstocks. Therefore, this work explores a non-catalytic pathway for effective demetallization of nitrogen-rich HTL biocrudes obtained from sewage sludge and cyanobacteria (generally referred as Spirulina algae). Herein, we utilized five different organic/inorganic acids and comprehensively documented the effect of acid washing on basic nitrogen containing compounds (NCCs), oxygenates and organometallics. HTL biocrudes before and after acid washing were characterized by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS). FTICR MS showed the presence of iron porphyrins in cyanobacteria biocrude, whereas no sign of metalloporphyrins was observed in sludge biocrude. Moreover, cyanobacteria biocrude mostly contains basic NCCs (N 1 and N 2 species), whereas sludge biocrude apart from basic NCCs mostly contain fatty acids (O 2 and O 4 species). Due to the presence and absence of metalloporphyrins, acid washing (0.1 M H 2 SO 4) showed ineffective demetallization (3.2 %) for cyanobacteria and effective demetallization 89.2 % for sludge biocrude. For cyanobacteria, 66.3 % demetallization was achieved at 10 M H 2 SO 4 which not only degrades the biocrude but also accounts for 35 % organic loss. However, O 1 -O 4 species in sludge biocrude represent acidic groups such as carboxyl groups; thereby, 20.1 % organic loss is encountered even at 0.1 M H 2 SO 4. For both biocrudes denitrogenation via acid washing remains unfeasible due to high organic loss. Present results indicate that a priori information about organometallics, NCCs, and oxygenates in a given biocrude could provide guidance to select and further optimize the demetallization process. [ABSTRACT FROM AUTHOR]

• A novel method for immobilization of metalloporphyrin (MP) in a nanocomposite system was developed. • Advanced nanocomposite combines the advantageous properties of magnetic nanoparticles and nanofibers. • Nanofibers allowing effective mass transport and has positive effect on the orientation of the attached MP. • The catalytic activity of metalloporphyrin in the nanocomposite system is tenfold higher than classic human liver microsome. In vitro mimicking of hepatic drug metabolism is a key issue in early-stage drug discovery. Synthetic metalloporphyrins show structural similarity with the heme type prosthetic group of cytochrome P450 as primary hepatic enzyme in oxidative drug biotransformation. Therefore, they can catalyze these oxidations. Concerning economical aspects and the poor stability of metalloporphyrin, their immobilization onto or into solid carriers can be promising solution. This study presents a novel immobilized metalloporphyrin nanocomposite system and its potential use as biomimetic catalysts. The developed two-step immobilization procedure consists of two main steps. First, the ionic binding of meso -tetra(parasulphonatophenyl) iron porphyrin onto functionalized magnetic nanoparticles is established, followed by embedding the nanoparticles into polylactic acid nanofibers by electrospinning technique. Due to the synergistic morphological and chemo-structural advantages of binding onto nanoparticles and embedding in polymeric matrices the biomimetic efficiency of metalloporphyrin can be remarkably enhanced, while substrate conversion value was tenfold larger than which could be achieved with classic human liver microsomal system. [ABSTRACT FROM AUTHOR]

Developing efficient catalysts with low cost and environmental friendliness for peroxymonosulfate (PMS) activation attracts broad interest. In this study, TiO 2 -hemin was prepared by immobilizing hemin on TiO 2 using a ball milling method, demonstrating 126.9-fold enhanced catalytic degradation efficiency compared with unsupported hemin in the PMS activation system, with 92.9% of 2,4,6-trichlorophenol (2,4,6-TCP) removed in 10 min. The superior performance is attributed to the strong interaction between TiO 2 and hemin, which induces the redistribution of the electron density of hemin molecules. In the TiO 2 -hemin/PMS system, sulfate radicals (SO 4 •-), hydroxyl radicals (•OH), singlet oxygen (1O 2), and superoxide radicals (O 2 •-) were identified, which only played a minor role in the elimination of 2,4,6-TCP. Instead, high-valent iron-oxo species were proposed and identified as the primary active species. This study provides a facile strategy to enhance the activity of the biomimetic catalyst and offers insight into the catalytic mechanism of iron porphyrin with PMS activation. [Display omitted] • A novel and facile strategy was proposed to enhance the catalysis of hemin. • Removal of 92.9% 2,4,6-TCP was achieved in 10 min by 20 mg/L TiO 2 -hemin. • Catalytic activity of TiO 2 -hemin was enhanced by 126.9-fold compared to hemin. • High-valent iron-oxo complex was the dominated species for 2,4,6-TCP degradation. • Electrons transfer from hemin to TiO 2 , promoting the generation of active species. [ABSTRACT FROM AUTHOR]

A new NMOFs-NADH model (UiO-66-NADH) had been designed and synthesized utilizing the hole-embedding block strategy for self-adaptive pore radius to FA, and could selectively capture and confined reductive remove of FA as a good donor of hydrogen proton in aqueous and gaseous phases. With the catalysis of tetra(carboxyphenyl)porphyrin iron (Ⅱ) (Fe-TCPP), UiO-66-NADH could selectively convert FA to methanol deeply and efficiently up to 98.6% within 40 min. In addition, the regeneration of UiO-66-NAD+/UiO-66-NADH was performed by g-C 3 N 4 via photocatalysis, and the recycled UiO-66-NADH still had high reduction activity after three cycles. While, a fixed bed reactor filled with UiO-66-NADH/Fe-TCPP mixture was employed for the selective absorption and removal of gaseous FA, also in the aqueous solution of some real samples. These results demonstrated that UiO-66-NADH/Fe-TCPP system had a great potential in environmental protection. The hole-embedding block strategy could be extended to related applications in air purification and environmental protection. [Display omitted] • A novel NMOFs-NADH (UiO-66-NADH) had been developed for the selective capture and confined reduction of formaldehyde. • The reduction rate of FA was up to 98.6% by UiO-66-NADH, with the catalysis of Fe-TCPP. • The recycling of UiO-66-NADH had been realized by the photocatalysis of g-C 3 N 4. • UiO-66-NADH/Fe-TCPP mixture was filled into a fixed bed reactor to capture the gaseous FA. • UiO-66-NADH/Fe-TCPP had been employed for the practical removal of FA in real water samples. [ABSTRACT FROM AUTHOR]