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Because of their large specific surface area, high porosity, changeable pore size, and ordered pore arrangement, metal–organic frameworks (MOFs) are emerging as electrocatalysts in various fields of energy resources and bio-sensors. In this work, we report a one-pot synthesis of trimetallic MOFs (Co–Ni–Al-MOFs), as well as bimetallic MOFs (Co–Ni-MOFs, Co–Al-MOFs, and Ni–Al-MOFs) using Co, Ni, and Al metal salts and BTC and 4,4′-bipyridine as linkers, their characterization for surface morphology, functional group and elemental analysis using various analytical techniques and explored them as tri-modal catalysts for thiophene electrooxidation, water splitting and chemical reduction of 4-nitrophenol (4-NP). Electrochemical studies using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) on Co–Ni–Al-MOFs showed the lowest onset potential of 1.36 V with a lower Tafel slope of 181 mV dec−1 and charge transfer resistance value (Rct) of 447 Ω for the effective electrooxidation of thiophene. Further catalytic activity studies towards water splitting revealed that Co–Ni–Al-MOFs displayed superior catalytic activity towards the HER and the OER at lower overpotentials of 174 and 220 mV with Tafel slopes of 108 and 97 mV dec−1 respectively, compared to other bimetallic MOFs with excellent long-term stability, as revealed by chronoamperometry (CA). The high catalytic activity of Co–Ni–Al-MOFs may be associated with their larger surface area and higher pore volume than those of the other bi-metallic MOFs, as studied by BET analysis, leading to innumerable redox-active sites towards electrochemical processes. Moreover, the catalytic activity of the as prepared catalysts was assessed towards the reduction of 4-NP to 4-aminophenol (4-AP), where Co–Ni–Al-MOFs exhibited exceptional activity with a minimum reduction time of 8 min bearing a high rate constant value. [ABSTRACT FROM AUTHOR]

Five new tricompartmental ligands, each having three tridentate dibasic ONO sites, have been obtained from the condensation of benzene-1,3,5-tricarbohydrazide (bthz) and 4-formyl-5-pyrazolone H6btzh(fp)3 (I), 4-acetyl-5-pyrazolone H6bthz(mp)3 (II), 4-propionyl-5-pyrazolone H6bthz(ep)3 (III), 4-butyryl-5-pyrazolone H6bthz(pp)3 (IV) and 4-benzoyl-5-pyrazolone H6bthz(php)3 (V). The reaction of I–V with [MoVIO2(acac)2] (Hacac = acetylacetone) leads to the formation of tris{cis-[MoO2]} complexes [{MoVIO2(H2O)}3bthz(fp)3] (1), [{MoVIO2(H2O)}3bthz(mp)3] (2), [{MoVIO2(H2O)}3bthz(ep)3] (3), [{MoVIO2(H2O)}3bthz(pp)3] (4) and [{MoVIO2(H2O)}3bthz(php)3] (5) having C3 symmetry. All ligands and complexes are characterized by various techniques: FT-IR spectroscopy, UV/Visible, NMR (1H and 13C), elemental analysis and thermal studies. X-Ray diffraction studies of complexes 2–5 confirm their distorted octahedral geometry, where each pocket of ligands coordinates through the enolate oxygen (of pyrazole), enolate oxygen (of hydrazide), and azomethine nitrogen atoms. Catalytic potentials of these complexes were achieved for the (i) oxidation of 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone (vitamin K3), (ii) oxidation of different olefins, and (iii) oxidative bromination of various phenol derivatives, including thymol. As high as 99% selectivity of 2-methyl-1,4-naphthoquinone has been obtained in high yield, while the selective olefin epoxidation resulted in the corresponding epoxide. The high yield of brominated products catalyzed by these complexes signifies them as useful functional models of vanadium-dependent haloperoxidases. [ABSTRACT FROM AUTHOR]

The paper reports on multicomponent (Ziegler) catalytic systems based on acetylacetonate complexes of cobalt, nickel or palladium and various aluminum-containing cocatalysts of general formula M(acac)2–Red (where M = Co, Ni, Pd; Red = AlEt3, LiAlH4, AlEt2(OEt), LiAlH(tert-BuO)3), which are active in alkenes hydrogenation under mild conditions (T = 30 °C, P = 2 atm). The key features (size, composition, nature of the ligand shell) of metal-containing nanoscale particles formed during the interaction of the initial components under inert medium and hydrogenation catalysis are considered. Also, the dynamics of the reaction solution changes in the course of catalytic processes as well as the kinetic parameters (activity, productivity, selectivity) of alkenes hydrogenation are described. The models of nanoparticles formed under the hydrogenation catalysis conditions during the interaction of M(acac)2–Red (where M = Co, Ni, Pd; Red = AlEt3, LiAlH4) are discussed. The role of proton-donor compounds (contained in the initial complexes of transition metals or specially introduced into the reaction systems) in the formation of catalytically active sites is explained. In particular, it is shown that the activating effect of these compounds is associated with alcoholysis of the cocatalyst and products of its catalytic decomposition, which are located on the surface of transition metal nanoparticles. A general scheme of activation of the [M]n particles formed by the interaction of M(acac)2 with AlEt3 (M = Ni and Co) is presented. The concept for the directed design of Ziegler catalytic systems is proposed. In order to evaluate the application scope of this concept, the reasons of different catalytic activity and productivity of bimetallic nickel–copper catalysts of the same composition, obtained by sequential and simultaneous reduction of Ni(acac)2 and Cu(acac)2 by LiAlH4, are revealed. In addition, a number of priority issues that should be addressed are discussed to highlight the prospects for the further development of this field of catalysis. [ABSTRACT FROM AUTHOR]

In this paper, a simple colloidal crystal-templating method assisted by a hydrothermal process has been proposed to prepare novel three-dimensionally ordered macroporous (3DOM) TiO2@nanosheet SnS2 heterojunction photocatalysts. The photoactivities of all the obtained samples were measured by the photodecomposition of rhodamine B (RhB), the photoreduction of Cr(vi) and photocatalytic hydrogen generation from water splitting. In comparison with pure SnS2 nanosheets and 3DOM TiO2, the 3DOM TiO2@SnS2 sample with a Sn/Ti molar ratio of 7.5 : 100 showed the highest photocatalytic activity for wastewater purification (kapp for RhB solution = 0.035 min−1 and for Cr6+ solution = 0.0845 min−1) and hydrogen generation under visible light irradiation. By means of ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, transient photocurrent spectra, electron paramagnetic resonance (EPR) measurements and photocatalytic experiments, a suggested mechanism for the charge generation and transfer in the 3DOM TiO2@nanosheet SnS2 heterojunction was proposed. The improved charge separation and enhanced photocatalytic activity for the as-prepared TiO2@SnS2 composition can be attributed to the well-defined 3DOM heterojunction structure and the spatial transfer of the visible-light excited high energy electrons of SnS2 to TiO2. This work will provide a novel route to prepare highly active heterojunction photocatalysts and a new insight into the study of electron migration paths in TiO2@SnS2 composites. [ABSTRACT FROM AUTHOR]

The mechanisms of Cu(II)/DBU-catalyzed carboxylation of homopropargylic amines with CO2 to construct 6-methylene-1,3-oxazin-2-ones are studied via density functional theory. The calculations suggest that Cu(II) catalysts exhibit a positive effect on the process of intramolecular cyclization, and the catalytic activities of which are determined by their coordination abilities ((DBU)CuCl2 < CuCl2 < [(DBU)CuCl]+). Furthermore, three roles of DBU are revealed in this study: (a) DBU acts as the proton-acceptor to capture a proton of homopropargylic amines. (b) DBU attacks CO2 to form DBU-CO2 as the nucleophilic agent, and then DBU-CO2 assists the H+ shift as the proton shuttle. (c) DBU serves as the ligand replacing one Cl− anion of CuCl2, forming the activated species [(DBU)CuCl]+. Besides, the theoretical study well explains the selectivity of Cu(II)-catalyzed reactions (6- vs. 7-membered cyclization), and the 6-membered products are found to be formed selectively. Overall, our work reproduces the experimental results well and provides an indispensable understanding of CO2-conversion to synthesize various high-value chemicals with the assistance of a catalytic system combining transition-metal catalysts and organic bases. [ABSTRACT FROM AUTHOR]

UiO-66 (UiO = University of Oslo) metal–organic frameworks (MOFs) exhibit high thermal and chemical stability, large surface area, and defined pore shape and size. On the other hand, Meerwein–Ponndorf–Verley (MPV) reduction is a selective hydrogenation reaction of carbonyl group through hydrogen transfer between ketones (aldehydes) and alcohols. Herein, in this work, a Hf(IV)-based UiO-66 MOF called CSMCRI-KNC (CSMCRI-KNC = Central Salt and Marine Chemicals Research Institute-Krishnath College) was synthesized using a 2-((2-hydroxy-4-methoxy-benzyl)amino) terephthalic acid linker via the solvothermal procedure. The guest-free form of CSMCRI-KNC (called CSMCRI-KNC′) was successfully employed as a reusable heterogeneous catalyst for the hydrogen-transfer reaction between carbonyl compounds and alcohol (isopropanol). The catalyst showed a high yield, high conversion, broad substrate scope, and high stability on the MPV reduction reaction. Interestingly, the catalyst was size-selective too. The catalytic performance of CSMCRI-KNC′ was compared with its Zr analog, UiO-66-NH2(Hf), UiO-66-NH2(Zr), UiO-66(Hf), and UiO-66(Zr). Interestingly, our developed catalyst showed much better activity compared to the others. The systematized research discovered that the excellent performance of CSMCRI-KNC′ predominantly originated from the more positively charged Hf(IV) species of [Hf6(OH)4(O)4]12+, which could boost the activation of the carbonyl group and instantaneously endorse the hydrogen-transfer process assisted by the available basic sites on CSMCRI-KNC′. The incorporation of the functional group also contributed to the excellent catalytic performance of CSMCRI-KNC′. Notably, the preparation of CSMCRI-KNC′ avoided the utilization of an expensive organic linker, and the prepared CSMCRI-KNC′ showed superior or similar catalytic activity than most reported Zr/Hf-containing catalysts, meaningfully empowering it to be a more practical option in the field of catalysis, and hydrogen transfer reactions. [ABSTRACT FROM AUTHOR]

In this work, two ordered mesoporous catalysts with different confined structures were successfully constructed for the catalytic combustion of propane. Notably, framework-confined Pt/Ti0.1AlOy-EISA catalysts were prepared using a one-step evaporation-induced self-assembly (EISA) technique, and we observed that the 0.3%Pt/Ti0.1AlOy-EISA catalyst exhibited superior catalytic activity for propane oxidation due to the dual effects of the dispersion of Pt nanoparticles and abundant surface adsorbed oxygen species (Oads). To further investigate the influence of the location of the active sites, we also prepared pore-confined Pt/Ti0.1AlOy-EISA catalysts, and it was verified that the framework-confined catalyst (0.3%Pt/Ti0.1AlOy-EISA) shows better activity and thermal stability than the pore-confined 0.3%Pt/Ti0.1AlOy-VI catalyst under the same Pt loading. Through a series of characterization studies, it is considered that the framework-confined 0.3%Pt/Ti0.1AlOy-EISA catalyst has higher Pt dispersion than the pore-confined 0.3%Pt/Ti0.1AlOy-VI catalyst. Interestingly, the pore-confined catalyst has better water and sulfur resistance than the framework-confined catalyst, because the pores protect the active sites from being covered with sulfate to some extent. The sulfate increases the acidity of the catalyst, thereby improving the water and sulfur resistance of the 0.3%Pt/Ti0.1AlOy-VI catalyst. The reaction mechanism of the catalytic combustion process of propane was analyzed via in situ DRIFTS experiments, and the Langmuir Hinshelwood (L-H) mechanism was proposed to be the possible reaction mechanism. [ABSTRACT FROM AUTHOR]

The MOF Fenton catalyst (MIL-101(Fe)) was developed and used for the efficient catalytic wet peroxide oxidation (CWPO) of metronidazole (MNZ) wastewater at a low reaction temperature. MIL-101(Fe) was characterized by XRD, SEM, FT-IR spectroscopy, and XPS. The catalytic activity of MIL-101(Fe) was investigated by CWPO of metronidazole wastewater with a high concentration of 200 mg L-1. In particular, the effects of calcination temperature (300-500 1C), degradation temperature (30-60 1C) and catalyst dosage (25-100 mg in 500 mL wastewater) on the CWPO of metronidazole wastewater were studied. The characterization results certificated the successfully synthesis of MIL-101(Fe), and the XPS analysis showed the valence state of the Fe species affected by the calcination temperature, while FT-IR results further demonstrated the structural and thermal stability of the catalyst. The MIL-101(Fe) Fenton catalysts exhibited excellent catalytic activity in the simulated MNZ wastewater, which was fast and completely degraded (XMNZ = 100%, XH2O2 = 83%, in 20 minutes). The MIL-101(Fe) catalysts retained high activity even at low temperatures (40 1C) and low catalyst usage (25 mg in 500 mL wastewater). The catalytic activity of MIL-101(Fe) was affected by the valence state of the Fe element, which was proved by the XPS results. The catalytic activity of Fe3+ in MIL-101(Fe) is higher than the Fe3+ in Fe2O3. MIL-101(Fe) is a potential energy-efficient Fenton catalyst for the degradation of nitroimidazole antibiotics in the environmental field. [ABSTRACT FROM AUTHOR]

Li–S batteries have attracted tremendous attention due to their relatively high theoretical energy density and low-cost raw materials. Unfortunately, their commercial market has always been challenged by the infamous/notorious shuttle effect of soluble lithium polysulfides. Defect engineering, like vacancy adjustment, which can change the surface adsorption and catalytic processes, has been acknowledged as an efficient strategy for taming the above issue. However, how vacancies affect the adsorptive and catalytic activity of transition metal carbides used in Li–S batteries has been rarely reported. Herein, first-principles calculations are performed to reveal that the introduction of Ni vacancies (NiVs) in Ni3ZnC0.7 can trigger the redistribution of electrons and improve the surface polarity, promoting chemisorption and thus effectively restraining the shuttle effect. More importantly, the upshift of the p-band center and the enhanced diffusion of Li+ can accelerate redox kinetics. Li–S batteries using commercial polypropylene separators decorated with NiVs–Ni3ZnC0.7 exhibit an outstanding cycling performance. This work provides a unique perspective on manufacturing high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]

Crystalline Pd7P3 and Pd3P0.8 nanoparticles (NPs) formed when palladium(II)-complexes (1 and 2) of (P, N) ligand [3-(diphenylphosphino)propan-1-amine] L1 and (P, N, O−) ligand [2-(((3-(diphenylphosphino)propyl)imino)-(phenyl)methyl)phenol] L2 were thermolyzed in a mixture of oleylamine (1 g) and oleic acid (6 mL), respectively. These NPs were characterized by powder-XRD, SEM and TEM. L1 and L2 and their Pd(II)-complexes (1 and 2) were characterized by multinuclear NMR. The complexes were also characterized with single crystal X-ray diffraction. The L1 coordinates with Pd(II) in a bidentate mode through P and N forming a six-membered chelate ring in 1. The ligand L2 coordinates with Pd in a monoanionic tridentate (P, N, O−) mode, which results in the formation of two six-membered chelate rings. The geometry around Pd in the two complexes is nearly square planar. The Pd–P bond lengths in 1 and 2 were found to be 2.225(2) and 2.234(16) Å, respectively. The Pd7P3 and Pd3P0.8 nano-phases, and their precursor complexes 1 and 2, were explored for their activity for catalyzing Suzuki–Miyaura coupling. The NPs were found to be less active as a catalyst for Suzuki coupling than the parent complexes. Both 1 and 2 showed good catalytic activity for Suzuki–Miyaura coupling of aryl bromides, which followed the order 2 > 1, i.e. it increases with dentate character. The catalysis with complexes 1 and 2 occurs via the formation of Pd-NPs associated with a ligand or its fragments as evidenced by TEM and SEM studies. NPs obtained from 2 have a higher percentage of P, which probably makes them more efficient. The Hg and PPh3 poisoning tests support the molecular nature of the catalysis. Three phase tests carried out with 1 and Pd7P3 reveal that the catalytic action of the complexes, as well as the NPs, involves both homogeneous and heterogeneous processes. [ABSTRACT FROM AUTHOR]

The development of highly efficient electrocatalysts for urea oxidation reaction (UOR) is crucial for reproducible and clean energy technologies. Herein, dual-phased nickel-based cost-effective catalyst nickel phosphide (Ni2P)-nickel metaphosphate (Ni2P4O12) microspheric nanoparticles were fabricated through a two-step hydrothermal-phosphorization process by preciously controlling the feeding ratios of the Ni precursor and the P source. It merely needs a potential of 1.35 V vs. RHE to deliver a current density of 10 mA cm−2 with a small Tafel slop of 55 mV dec−1 and maintains high catalytic activity for 10 h in 1.0 M KOH with 0.33 M urea solution. The synergy effect and modulation of the electronic structure between Ni2P and Ni2P4O12 could be the reason for the good UOR performance. This work provides a new perspective for the further design of high-performance electrocatalysts in diverse energy fields. [ABSTRACT FROM AUTHOR]

p-Nitrophenol (PNP) is an important pesticide intermediate, and is also a water pollutant that is extremely harmful to personal health. It can be converted to p-aminophenol (PAP) through selective catalytic hydrogenation reduction. This work reports that the Co/CN-x (x is the pyrolysis temperature) catalysts derived from the precursor Co-ZIF-9 could catalyze highly selective hydrogenation of PNP with H2 to PAP. The obtained N-doped semi-graphitic C loaded with a metallic Co (Co/CN) catalyst had an extraordinary morphology and exhibited excellent catalytic hydrogenation activity. The size effect of Co NPs dispersed on nitrogen–carbon materials played a critical role in promoting the reaction efficiency. It was found that the conversion of PNP reached 100% and the selectivity of PAP was 98.5% over Co/CN-350 under mild reaction conditions. In addition, Co/CN-x catalysts also displayed excellent substrate tolerance and good recyclability with a catalytic performance remaining between 97.4% and 100% with 14 recycles. This work not only provides a new idea for the application of environment-friendly Co-based catalysts, but also opens up a suitable catalytic route for selective hydrogenation of nitrophenols. [ABSTRACT FROM AUTHOR]

The importance of photocatalytic hydrogen evolution is increasing in energy research and environmental catalysis. Co-MOF, a metal–organic framework compound with a zeolite topological structure, has the advantage of being a semiconductor in photocatalytic applications. The new composite materials constructed by coupling Co-MOF with traditional semiconductors will significantly stimulate the potential of photocatalysis due to the construction of a heterogeneous interface. We accurately controlled the growth of Co-MOF with different morphologies by adjusting the ratio of raw materials. With the increase of dimethylimidazole, hexagonal prism morphology (Co-MOF-H), leaf morphology (Co-MOF-B), and Daisy morphology (Co-MOF-D) were successively synthesized. The experimental results show that H-g-C3N4 has the best catalytic activity when adsorbing hexagonal prism Co-MOF. When the ratio of H-g-C3N4 reached 125 mg, the optimal hydrogen evolution activity reached 1033 μmol g−1 h−1. Various characterization methods were used to explain the influence of morphology regulation on the hydrogen evolution ability of Co-MOF and explore the mechanism of hydrogen evolution of Co-MOF/H-g-C3N4 composite catalysts. [ABSTRACT FROM AUTHOR]

In this study, different proportions of Pd/Sn of PdSn/C, PdSn2/C and PdSn4/C catalysts were prepared by a simple mixed calcination method. The characterization methods, such as BET, XRD, TEM and XPS, were used to study a series of Pd–Sn alloy catalysts. The catalytic activity of Pd–Sn alloy catalysts was investigated by catalytic hydrogenation of 4-nitrophenol. The experimental results show that the PdSn4/C catalyst shows good catalytic activity (k = 0.38 × 10−2), which may be due to the synergistic effect between the Pd and Sn, making the bimetallic alloy more evenly dispersed. Pd has a greater positive charge, affecting the adsorption energy of the catalyst for reactants and products. [ABSTRACT FROM AUTHOR]

The design and development of a low-cost and sustainable catalytic system to replace expensive Pd-catalysts for the Suzuki cross-coupling reaction is one of the major challenging areas of research in synthetic organic chemistry. Cross-coupling reactions with good yield in the presence of the Cu-based monometallic catalyst at room temperature have not been realized in previous works. We herein report the fabrication of a novel "single-atom" Cu catalyst (Cu-TAPB-BTDA-COF) for the Suzuki-coupling reaction at room temperature. The catalyst was obtained by post-synthetic metalation of the COF, synthesized by the combination of 4,4′-(benzothiadiazole-4,7-diyl)dibenzaldehyde (BTDA) and 1,3,5-tris-(4-aminophenyl)-benzene (TAPB). Cu-TAPB-BTDA-COF shows excellent catalytic activity for the Suzuki cross-coupling reaction, which is able to effectively promote the Suzuki cross-coupling reaction under mild reaction conditions (room temperature, a nontoxic solvent, and air atmosphere). In addition, the catalyst could be recycled and reused multiple times without the loss of catalytic activity. Compared with other Cu-based catalysts, our COF-based Cu catalyst simultaneously demonstrates excellent performance and recyclability. [ABSTRACT FROM AUTHOR]

Defect engineering is a promising strategy that essentially tailors the specific surface area, energy band structure and photocatalytic properties of catalysts. Herein, a series of oxygen defect modified polyimides (PI-NaHCO3 (1 : 1, 1 : 4, and 1 : 8)) containing triazine rings have been synthesized via thermal polymerization by introducing an inorganic foaming agent NaHCO3 into the synthesis of classical polyimide (PI). During the polymerization and washing process, a large amount of gas generated by NaHCO3 breaks the imide bond connections in PI, resulting in the formation of oxygen defects. The experimental results revealed that with the introduction of oxygen defects, the band gap of PI broadened, and the absorption band edge exhibited a certain blue shift. However, the separation and transmission of photogenerated carriers were significantly enhanced, and the radiation recombination has been inhibited. Therefore, the photocatalytic activity of samples was significantly improved. Among them, PI-NaHCO3 (1 : 4) shows the optimal catalytic activity in photocatalytic benzylamine oxidation and photocatalytic hydrogen evolution experiments. Under irradiation using a 420 nm LED (10 W), the conversion and selectivity of benzylamine to corresponding imine are more than 99%. This work provides a new way for the design of defective polyimide materials. [ABSTRACT FROM AUTHOR]

The development of efficient, durable and economical catalysts based on non-precious metals for the controllable and fast hydrogen evolution from chemical hydrogen storage materials is highly desirable for the hydrogen economy. Herein, we introduce an advanced catalytic system by in situ encapsulating cobalt phosphide (CoP) nanoparticles into a quasi-metal–organic framework (quasi-Co-MOF-74) through a smart pyrolysis method. The designed synergic structure of CoP@quasi-Co-MOF-74 facilitates the efficient adsorption and activation of reactants, and achieves superior catalytic activity for the dehydrogenation of ammonia borane (AB). The extremely high hydrogen generation rate (HGR) of 9790 mL min−1 gcat−1 achieved by this catalytic system is 13.1, 4.4, and 46.5 times higher than that of quasi-Co-MOF-74, CoP, and CoP@C counterparts, respectively. Furthermore, CoP@quasi-Co-MOF-74 also delivers a high turnover frequency (TOF) of 55.9 min−1 and a low activation energy of 38.22 kJ mol−1 for the catalytic hydrolysis of AB, which compares favorably to most of the previously reported transition metal phosphide and cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

Two lanthanide-coordination polymers (Ln-CPs) containing benzophenone-4,4′-dicarboxylate (bpndc2−) linker, namely [Er2(bpndc)3(DMF)2] (1) and [Yb2(bpndc)3(DMF)2] (2) were synthesized and characterized using X-ray crystallography and spectroscopic methods. The topological analysis revealed that both compounds are chiral three-dimensional uninodal 5-connected net of type yfh. These Ln-CPs showed good stability and thus were used as heterogeneous catalysts for the acetalization of glycerol. This study provides some further evidence supporting the effectiveness of Ln-CPs as potential Lewis acid catalysts for chemical transformations. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction reaction (CO2RR) is a valid strategy for the conversion of CO2 into valuable fuels and chemical products, thereby alleviating the energy crisis and environmental problems. In this work, the reaction mechanism of the CO2RR has been studied on the two dimensional MOFs TM–PTC (TM = Sc–Zn, Y–Mo, and Ru–Ag; PTC = 1,2,3,4,5,6,7,8,9,10,11,12-perthiolated coronene) by using the density functional method. Our results showed that for the studied catalysts, the main products are CH4 and HCOOH. Mo–PTC has the best catalytic activity for the CO2RR in producing CH4. Axial oxygen modified TM–PTC, i.e., TM–O–PTC shows different catalytic behavior compared with those without axial oxygen in producing CH4. The inactive catalyst Nb–PTC for CH4 becomes active after modification with an axial oxygen ligand. Zn–PTC and Mn–PTC are the promising catalysts for the CO2RR in producing HCOOH. The solvent effect plays an important role in both the reaction mechanism and catalytic activity. We hope that this work can provide a new avenue for the development of 2D MOF type CO2RR electrocatalysts. [ABSTRACT FROM AUTHOR]

Mononuclear nonheme copper(II) compounds [Cu(BQEN)(CH3CN)]2+1 and [Cu(BQPN)(CH3CN)]2+2 (BQEN = N,N′-dimethyl-N,N′-di(quinolin-8-yl)ethaneane-1,2-diamine; BQPN = N,N′-dimethyl-N,N′-di(quinolin-8-yl)propane-1,2-diamine) were synthesized and characterized by elemental analysis, ESI-MS, EPR, and single-crystal X-ray diffratrometry. Compound 1 crystalized in the P1¯ space group, while 2 crystallized in the P21/n group. Compounds 1 and 2 exhibited distorted square pyramidal geometry, which deviated interestingly by 4.8% and 46.0% from a regular square pyramidal structure in 1 and 2, respectively. This was attributed to the marginal increase in the carbon chain backbone of the ligand in 2. Compounds 1 and 2 were used in the aerial oxidation of 2-aminophenol (H2AP) to 2-amino-phenoxazine-3-one (APX), which revealed phenoxazinone synthase activity. DFT steric maps were utilized to understand the catalytic activity of 1 (% Vbur, 71.3%) and 2 (% Vbur, 75.6%). The current results clearly demonstrate an interesting structure–function relationship based on the effect of the ligand backbone on the geometry. [ABSTRACT FROM AUTHOR]

Nickel-based (Ni-based) compounds have been regarded as one of the most potential electrocatalysts for water splitting due to their tunable d-band electronic structures. However, the local structures of Ni-based electrocatalysts would change in situ during the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which makes it difficult to identify and design active structures. In this study, we studied metallic Ni3Se2 films as model catalysts to figure out the structural change rules during HER and OER processes. According to the operando X-ray absorption fine structure (XAFS) spectroscopy and other experimental results, during the HER process, the active Ni sites at the surface tended to adsorb hydroxyl to form local Ni–OH environments and trigger further water dissociation with the assistance of Se sites as hydroxyl acceptors; during the OER process, the valence states of Ni increased with the increase in potential, proving that high-valence Ni centers in NiOOH activated species are beneficial in boosting OER catalytic activity. [ABSTRACT FROM AUTHOR]

The development of substantial, environment-friendly and low-cost electrocatalysts for an efficient oxygen reduction reaction (ORR) is essentially important for the production and storage of green energy which has sparked the curiosity of researchers for scalable production of metal-free electrocatalysts from biowaste. We report an easy transformation of chestnut-derived biowaste into reduced graphene oxide (rGO) and pyridinic-N-dominated nitrogen-doped rGO (NCS-rGO). The synthesized catalyst exhibits better ORR activity with an onset and half-wave potential of 0.93 V and 0.86 V, respectively, along with a high diffusion-limiting current density of 5.05 mA cm−2. Under alkaline conditions, we found that NCS-rGO shows an unusually high electrocatalytic activity that is superior to that of the commercial 20% Pt/C catalyst. More notably, the NCS-rGO-based ORR electrocatalyst manifests higher methanol tolerance, without deterioration in catalytic activity even in the presence of significant amount of methanol, outperforming the current state-of-the-art Pt electrocatalyst. Density functional theory (DFT) studies illustrate that pyridinic N is a decisive part of NCS-rGO to achieve the best ORR performance. [ABSTRACT FROM AUTHOR]

The exploration of efficient, stable, and economical electrocatalysts for oxygen evolution reaction (OER) is of great significance and challenge for the development of renewable energy. A series of Ni-based layered double hydroxides (LDHs) have been explored as promising electrocatalysts for OER on account of their earth abundance, low overpotential, and super stability. However, the low electrical conductivity of LDHs cannot satisfy the progressive requirements of water splitting. Herein, we introduce a template strategy to synthesize trimetallic nickel-chromium LDH–cobalt (NiCr-LDH–Co) nanosheets on nickel foam (NiCr-LDH–Co/NF) without any binders as efficient catalysts for OER. Compared with the reported NiCoCr-LDHs synthesized by one-step, our NiCr-LDH–Co/NF delivered a lower overpotential of 229.4 mV at 50 mA cm−2, which is even lower than that of all the reported bimetallic nickel-based LDHs (NiFe-LDH, NiCo-LDH, NiMn-LDH, NiTi-LDH, NiV-LDH, etc.) and the precious RuO2 catalyst. Furthermore, the NiCr-LDH–Co/NF was maintained for at least 24 h at a high current density of 50 mA cm−2 without much deviation in 1 M KOH solution. The effective integration of the layered structures of LDH and the high electronic conductivity of the Co element endow NiCr-LDH–Co/NF remarkable catalytic ability for the OER process. Furthermore, the strategy expands the possibility for improving the catalytic activity of trimetallic LDHs as OER catalysts. [ABSTRACT FROM AUTHOR]

Conventional metal and cermet cathodes are easily oxidized during CO2 electrolysis, which seriously affects the electrolysis performance of electrolysis cells. The excellent durability and low cost of ceramic cathodes make them a promising alternative electrode. However, their catalytic activity is limited. In this work, we prepared a series of perovskite materials La0.6Sr0.4Cr1−xFexO3−δ (LSC1−xFx, x = 0–1) by synergistic doping at the B site to improve the catalytic activity. Replacing Cr with Fe can increase the concentration of low-valent Fe ions linked to oxygen vacancies, which leads to an increase in oxygen vacancies and thus improves the activity of CO2 electrolysis. Among the LSC1−xFx (x = 0–1) cathode materials, the LSC0.25F0.75 sample exhibits the highest electrochemical catalytic activity with a CO production rate of 5.32 mL min−1 cm−2 at 1.6 V and 850 °C, which is about 5 times that of other LSC cathode materials. In addition, its current efficiency can reach 96.4% during electrolysis of CO2. The electrolytic performance remained stable during the high temperature test for up to 100 h, further demonstrating its excellent thermal stability. [ABSTRACT FROM AUTHOR]

Preparation of macroscopic objects using covalent organic frameworks (COFs) is challenging. However, it is imperative to fully utilize their customizable pore structure to synthesize nanomaterials with controlled size and dispersion. Here, CS/ZIF-8@COF microcapsules were successfully synthesized by growing COFs in situ within the pore channels of honeycomb chitosan microcapsules. COFs of different structures could grow uniformly and form fibrous or vesicle-like structures on the inner walls of chitosan microcapsules. COFs can significantly prevent chitosan from swelling in water and enhance the stability of CS/ZIF-8 microcapsules. The inherent porosity of COFs facilitates the immobilization and dispersion of palladium nanoparticles, and a large number of N atoms in their structure effectively prevent the aggregation and shedding of palladium. The prepared CS/ZIF-8@COFa-4@Pd showed excellent catalytic activity in the reduction of p-NP (Kapp = 1.1 min−1) and the Suzuki coupling (TOF = 7.1 × 104) reaction. The CS/ZIF-8@COFa-4@Pd catalyst exhibited no obvious loss of catalytic activity after five repeated uses. [ABSTRACT FROM AUTHOR]

Dimethyldichlorosilane, which is the most important organic silicon monomer, can be prepared using a novel core–shell catalyst. However, the debate continues regarding its redistribution mechanism. In the current study, the redistribution mechanism catalyzed by the ZSM-5(5T)@MIL-53(Al) catalyst was theoretically studied via density functional theory on the level of M06-2X/def2-TZVP. Then, the catalytic performances of different active centers modified with AlCl3 were evaluated. The results showed that the active center of the former was Brønsted acid, while that of the latter modified by AlCl3 was Lewis acid. In addition, Lewis acid increased the catalytic activity in comparison with Brønsted acid. The calculations of activation energy, frequency vibrational analysis, bond order analysis, frontier molecular orbital theory, electronic localization function, and localized orbital locator analyses were in agreement with the said mechanism and results. [ABSTRACT FROM AUTHOR]

The rational design of efficient electrocatalysts for nitrogen reduction reaction (NRR) to produce NH3 under ambient condition is a longstanding challenge. The graphene-based single-atom catalyst (SAC) has been revealed as a promising candidate. Previous studies mainly focused on the metal center coordinated with N atoms, while those coordinated with other heteroatoms were rarely reported. Herein, we theoretically investigated the effect of oxygen coordination on the performance of vanadium (V) SAC embedded in graphene (VO4/G) towards NRR owing to the fact that V with less d electrons usually exhibits high chemical activity. It is revealed that VO4/G with good stability can efficiently convert N2 into NH3 through a distal mechanism with a low limiting potential of −0.60 V, which is superior to the experimentally synthesized FeN4/G and FeO4/G SACs. Moreover, the stronger adsorption of N2 than the H atom renders the high NRR selectivity of VO4/G against the competing hydrogen evolution reaction, and the rapid removal of the produced NH3 endows VO4/G with excellent recyclability. The good stability, high catalytic activity and selectivity, and excellent recyclability make VO4/G a prospective NRR catalyst. This work provides a promising NRR electrocatalyst awaiting experimental exploration and will stimulate further studies on other coordination atoms beyond N for graphene-based SAC. [ABSTRACT FROM AUTHOR]

Herein, a series of highly active K species-supported synergistically modified LaMnO3 (LM) catalysts were prepared by acid etching for soot oxidation. As shown in XRD, TEM and XPS results, appropriate etching hours could remove La atoms on A-sites and produce A-site defects without destroying the whole perovskite structure, which created more B-sites on terminated perovskite surfaces and promoted the activation of oxygen molecules through Mn4+/Mn3+ redox cycles, thus improving the catalytic activity for soot combustion. Based on this, further modification of the LM catalyst by introducing K could enhance the lower temperature reducibility of the catalyst, and promote more active oxygen species production through the interaction between potassium and LM support, thereby leading to a further improvement in catalytic performance, as confirmed according to XPS O 1s and H2-TPR results. Among all the as-prepared catalysts, the 15K/LM-2h catalyst exhibited favorable catalytic performance and stability, where the T90 values were 416 °C and 327 °C under loose and tight contact, respectively, and the Ea value was 64.2 kJ mol−1. This study provides a universal strategy for the development of high-performance catalysts for soot combustion with promising industrial application prospects. [ABSTRACT FROM AUTHOR]

Catalytic conversion of CO2 to CO (reverse water-gas shift reaction, RWGS) is one of the most promising technologies for CO2 resource utilization. In this work, a sulfur-containing zirconia supported nickel catalyst (Ni/ZrO2) was prepared to improve the CO2 conversion while adjusting the CO2 hydrogenation selectivity from CH4 to CO. The effect of support size (80 nm, 120 nm, 200 nm and 320 nm) on the catalytic performance of RWGS was investigated. The results showed that the Ni/ZrO2-80 sample with a smaller support size of 80 nm exhibited higher Ni dispersion and oxygen vacancy concentration, which not only exposed more active sites but also enhanced the adsorption and activation capacity of CO2. For these reasons, the CO2 conversion of 27.6% with 100% selectivity of CO was achieved over Ni/ZrO2-80, and no catalyst deactivation was observed during the stability test for 50 h. This work provides a new idea for designing the RWGS catalyst with an outstanding CO2 hydrogenation performance. [ABSTRACT FROM AUTHOR]

Constructing Ce-based catalysts with excellent catalytic activity and toxicity resistance is an effective strategy for the selective catalytic reduction of NO by NH3. Here, ordered mesoporous structured CexWy/TiO2/SBA-15(TS) catalysts with different Ti/Si molar ratios (2 : 6, 3 : 6, 4 : 6) as well as the Ce and W contents were prepared using the vacuum impregnation method. Among them, the prepared TS-3 (Ti : Si = 3 : 6) carrier had a regular ordered mesoporous structure, which could provide a better supporting space for the attachment of active ingredients. After the active species were introduced, with the help of a series of characterization analyses, it was found that the Ce10W2/TS-3 catalyst had a large specific surface area, where the active species were stably dispersed via the pore confinement effect of the ordered mesopores' structure, and the efficient charge transfer significantly enhanced its redox ability and surface acidity. In addition, the ordered pore structure protected the active sites from the competitive adsorption of water vapor and sulfur attack. Consequentially, the ordered mesoporous confined Ce10W2/TS-3 catalyst exhibited good catalytic performance in a wide temperature window, and its water and sulfur resistance was also enhanced to some extent. This work provided new insights into the design and synthesis of ordered mesoporous confined structure Ce-based catalysts for NH3-SCR applications. [ABSTRACT FROM AUTHOR]

Developing efficient, durable, and noble-metal-free electrocatalysts is considered the Holy Grail of sustainable hydrogen production through water splitting. In light of the potential importance of carbon components in low-cost electrocatalysis, various innovative synthesis strategies offering better structural integrity and facile electronic communication between the carbon component and catalytically active component are highly sought after. In coherence with this concept, N and S dual-doped carbon-armored Co9S8 (Co9S8@NSC) nanomaterials are synthesized via an improvised solid-state pyrolysis of Co(II) and sulphanilic acid adduct. The as-obtained nanomaterials furnish a bifunctional electrocatalytic activity for overall alkaline water splitting. In particular, Co9S8@NSC-8 (synthesized at 800 °C) shows impressive bifunctional activity with very low overpotentials of 267 and 120 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, corresponding to a current density of 10 mA cm−2. The catalyst supports rapid reaction kinetics for both HER and OER with respective Tafel slopes of 85 and 48 mV dec−1. The full-cell measurement with Co9S8@NSC-8 at both electrodes demonstrates a remarkable performance towards simultaneous HER and OER production, yielding a current density of 10 and 80 mA cm−2 at low potentials of 1.6 and 2.4 V, respectively. The degree of graphitization and the status of N and S doping in the carbon shell of Co9S8@NSC reasonably explain the catalytic activity they have acquired. In the long-term durability test, the catalyst retains its activity after 10 h of electrocatalysis, reflecting impeccable stability in an alkaline environment. The superior electrocatalytic activity of Co9S8@NSC materials is mainly attributed to a strong interfacial interaction between the Co9S8 cores and N,S-doped carbon shells. [ABSTRACT FROM AUTHOR]

Solar-driven photocatalytic H2O2 production with water and O2 is an environmentally friendly process for producing H2O2, an important chemical. Compared with traditional photocatalysts, covalent organic frameworks (COFs) have received extensive attention due to their tuneable composition and photoelectric structure at the molecular and nanoscale levels. Ligand functionalisation is an efficient strategy to modulate the properties and stability of COFs. Here, we synthesized a series of functionalised TAPB-PDA-X with various functional groups (X = H2, OH, OCH3, and CH3) for photocatalytic H2O2 production under visible light and investigated their morphology, light-absorption intensity, stability, catalytic activity and band gap. We found that the hydroxyl functional group modification TAPB-PDA-X can further improve its photocatalytic H2O2 production abilities. The photocatalytic H2O2 evolution over the TAPB-PDA-OH catalyst reached 2117.6 μmol g−1 h−1, and the apparent quantum yield (AQY) was 2.99% at 420 nm. The hydroxyl group in TAPB-PDA-X can enhance visible-light absorptions and improve the stability of photocatalytic H2O2 production. Mechanistic experiments illustrate that photocatalytic H2O2 evolution is a two-step single-electron reduction process. Our results offer new ideas for developing solar-driven metal-free photocatalysts. [ABSTRACT FROM AUTHOR]

The emergence of the "double carbon" era indicates more significant concerns in CO2 utilization. CO2 to methanol conversion is one of the most promising methods for converting CO2, but its extensive application is restricted by harsh reaction conditions. A photo-assisted reaction is expected to effectively alleviate the harsh reaction conditions and exhibits high catalytic activity. In this work, the contribution of photo-assistance was investigated in the CO2 reduction reaction over Cu–ZnO and Cu–ZnO–ZrO2 catalysts. Cu–ZnO–ZrO2 exhibits higher methanol selectivity (61.2%) than Cu–ZnO (34.2%), and methanol selectivity is further improved from 61.2% to 70.4% with the photo-assisted reaction. The superior performance of the Cu–ZnO–ZrO2 catalyst is due to the generation of more oxygen vacancies (Ov) on the ZnO surface, which reduce the bandgap of the catalyst and change the conduction band (CB) position. The generation of electrons is promoted under light irradiation, making the catalyst more favorable for the reduction of CO2 to methanol. Therefore, the effective reduction of CO2 to methanol is feasible on the photo-assisted Cu–ZnO–ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

Using two different metalloligands [NiLA] and [NiLB], developed using two different N2O2 donor Schiff bases, H2LA 6,6′-((1E,1′E)-((2,2-dimethylpropane-1,3-diyl)bis(azaneylylidene))bis(2-methoxyphenol) and H2LB 6,6′-((1E,1′E)-((2,2 (2-ethoxyphenol), two new tetra- and trinuclear heterometallic complexes, [(NiLA)2(CH3COO)2(SCN)2(Co)2] (complex 1) and [(NiLB)2(SCN)2Mn] (complex 2), have been synthesized. The two newly formed complexes have primarily been characterized using several spectroscopic techniques. According to the single-crystal structural study, the metalloligand portion is shared by both crystals. Complex 1 is a tetranuclear complex where Ni(II) is connected to Co(II) via acetate and phenoxide bridging, whereas complex 2 is a trinuclear complex where each Ni(II) center is coordinated to Mn(II) via phenoxide bridging only. It is interesting to note that the thiocyanate moiety in complex 1 is linked to Co(II), whereas in complex 2, it is linked to Ni(II) as a secondary anionic residue. Following structural analysis, both complexes were exposed to catecholase-like activity to test their ability to aerially oxidize 3,5-di-tert-butylcatechol. The calculated turnover numbers (Kcat) 355 h−1 and 286 h−1 for complexes 1 and 2, respectively, unveiled that complex 1 is more susceptible to this catalytic process. The generation of Ni(I) in complex 1 is more favorable than the formation of Mn(I) in complex 2 during catalysis and this is the factor responsible for the higher susceptibility of complex 1 towards the catalytic process. To determine whether both the studied complexes can function as effective Schottky devices, the band gap values for complexes 1 and 2 were used to calculate the diode parameters. The results show that complex 1 will function as a better Schottky device than the complex 2. [ABSTRACT FROM AUTHOR]

A new nanocomposite of β-Ni(OH)2 nanoparticles immobilized on cucurbit[6]uril, β-Ni(OH)2-CB[6], was designed and characterized using several physicochemical techniques, viz FTIR, PXRD, XPS, FESEM, HRTEM, EDAX, TGA, and ICP-OES. The nanocomposite was successfully applied as a heterogeneous catalyst in the synthesis of a series of pharmaceutically important quinazolines, in good to excellent yields (67–96%) and with high turnover numbers (TONs), via acceptorless dehydrogenative coupling (ADC) of alcohols with nitriles. To the best of our knowledge, this is the first report on the use of a heterogeneous catalyst in the ADC reaction between alcohols and nitriles to afford quinazolines. The catalyst could be reused up to four times with an insignificant decrease in its catalytic activity. The identity of all the isolated organic products were confirmed by 1H and 13C{1H} NMR studies. The striking features of the methodology are high atom economy, broad substrate scope and functional group tolerance, generation of non-toxic side-products, use of a cheap catalyst and stoichiometric reagents. The values of green chemistry matrices for the reaction were found to be in close proximity to the ideal values. [ABSTRACT FROM AUTHOR]

Efficient and durable methanol electro-oxidation catalysts in acidic media are essential for commercial applications of direct methanol fuel cells (DMFCs). In this work, PtCu nanoparticles are prepared via the wet chemical method for the oxidation reaction of the DMFC. The combination of Cu and Pt can effectively adjust the electronic structure of the catalyst and oxidize COads at a lower potential. Electrochemical tests show that PtCu nanoparticles have an excellent catalytic activity for methanol oxidation, where the peak current reaches 1010.41 mA mgPt−1, which is 3.1 times higher than that of the commercial Pt/C catalyst. In addition, the synthesis steps are simple, and the catalyst prepared using this method shows high activity and stability, thus creating conditions for realizing industrialized preparation. [ABSTRACT FROM AUTHOR]

Commercial applications of electrolytic water splitting require cost-efficient and active oxygen evolution catalysts. Nickel–iron (NiFe)-based compounds have attracted significant attention as oxygen evolution reaction (OER) catalysts due to their high catalytic activity. We develop a simple and easily controlled method by combining anodic fluoridation and cyclic voltammetry (CV) treatment to convert NiFe alloy to Ni/Fe hydroxide. A cracked layer structure of Ni/Fe hydroxide formed on the surface during the fluoridation of NiFe alloy and the CV process in KOH. The Ni/Fe hydroxide exhibits considerable OER activity with an onset potential of 1.47 V vs. RHE and a Tafel slope of 47 mV dec−1 in 0.1 M KOH. The electrode also shows an acceptable stability in alkaline media. The results indicate that anodic fluoridation and CV treatment are promising methods to form active layer structures of hydroxide on transition metals and their alloys, further increasing the electrocatalytic activity of the catalyst. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are one of the ideal functional materials for the oxygen evolution reaction (OER) because of their special configuration and good electrochemical activity. Incorporating different divalent and trivalent metals into layered double hydroxides (LDHs) is an effective way to induce defects and generate abundant oxygen vacancies and adjust the morphology of the materials and thus enhance the intrinsic catalytic activity of the materials. In this work, a nano-flower-like Mg-doped NiCo-LDH (denoted as NiCoMg-LDH) was synthesized by a solvothermal method, and the effect of the molar ratio of Mg, Co and Ni on the electrochemical activity of NiCoMg-LDH was explored. The results showed that NiCoMg-LDH with the optimum molar ratio (Ni : Co : Mg = 3 : 3 : 0.3) exhibited excellent OER catalytic activity in 1.0 M KOH, with an overpotential of only 229 mV at a current density of 10 mA cm−2, a small Tafel slope of 31.0 mV dec−1, and an electrochemically active surface area (ECSA) of 410 cm2. This work provides a facile but effective method to improve the OER performance of layered double hydroxides. [ABSTRACT FROM AUTHOR]

Cu/SBA-15 catalysts were prepared by the impregnation method using mesoporous siliceous SBA-15 as the support. The effects of different loadings of Cu/SBA-15 catalysts on the catalytic oxidation of NO were investigated. The physical and chemical properties of the Cu/SBA-15 catalysts were characterized by N2 adsorption/desorption, SEM, XRD, TEM, FTIR, XPS, H2-TPR and O2-TPD. The characterization results suggested that the incorporation of copper did not disrupt the ordered hexagonal mesoporous structure of SBA-15. A lower copper loading was beneficial for increasing the dispersion of CuOx on the surface of the support, thereby improving the activity of the catalyst. At loading above 10%, the CuOx material aggregated into CuOx clusters on the SBA-15 support and changed from an amorphous phase to a crystalline phase, reducing the catalytic activity. Moreover, the lower copper loading was beneficial for improving the reduction ability and desorption of surface chemisorbed oxygen of the catalyst. The experimental results indicated that 10% Cu/SBA-15 catalysts exhibited the highest activity, nearly 90% of NO conversion efficiency. [ABSTRACT FROM AUTHOR]

As a simple and promising hydrogen carrier, hydrogen production from formic acid (HCOOH) has been extensively investigated, owing to the properties of colorlessness, non-toxicity, and safety of formic acid. Palladium-based catalysts are commonly applied in thermocatalysis reactions, hydrogenation reactions as for example. A facile method is used to synthesize Pd/polypyrrole (Pd/PPy) catalysts. The catalytic activity of Pd/PPy from formic acid for hydrogen production was investigated. The support of catalysts were with two different state, one support of PPy was synthesized by chemical in situ polymerization, while the other was purchased. Using a collection of characterizations to determine the structure and morphology properties of as-prepared Pd/PPy catalysts, such as XRD, SEM, TEM, FT-IR, BET and XPS. The as-prepared Pd/PPy catalysts have a good catalytic activity for hydrogen production from formic acid. Meanwhile, Pd/PPy-S1, which support was synthesized by chemical in situ polymerization, has a better catalytic activity for dehydrogenation of formic acid. Apart from the different specific surface area and similar particle size of Pd ranging from 5 nm to 30 nm, the distinctive interaction of Pd and PPy results the different catalytic activity. We finally came up with a proposed possible reaction mechanism. This work provides some significant guidance in high efficiency catalysts development for hydrogen production from formic acid. [ABSTRACT FROM AUTHOR]

The application of zeolite imidazolate framework (ZIF)-based nanomaterials for oxygen reduction reaction (ORRs) and supercapacitors (SCs) is drastically confined by their quick aggregation and irreversible fusion of metal nanoparticles. Herein, the impact of using the mesoporous silica-protected calcination strategy on the CuFe-ZIF composite is studied. To this end, the CuFe-ZIF catalyst was first prepared and then covered by mesoporous silica (mSiO2). The acquired CuFe-ZIF@mSiO2 was pyrolyzed at 900 °C under an Ar atmosphere. After pyrolysis and acid etching, the Cu@Fe–N–C nanomaterial was formed. The synthesized samples were evaluated by physical and electrochemical tests. According to the results, Cu@Fe–N–C with mSiO2 protection exhibited better ORR catalytic activity with an onset potential of −0.04 V vs. Ag/AgCl compared to the unprotected sample (−0.17 V vs. Ag/AgCl). Besides, its average electron transfer number was found to be 3.55, indicating a 4-electron pathway for ORR. Furthermore, it offered excellent performance in a supercapacitor by applying the mSiO2 cover, and the specific capacitance value significantly enhanced from 191 F g−1 to 341 F g−1 at a current density of 1 A g−1. Therefore, it can be deduced that by employing the mesoporous silica covers during calcination process, the electrochemical properties of CuFe-ZIF-based materials can be considerably improved. [ABSTRACT FROM AUTHOR]

Recently, metal–organic framework (MOF)/peroxymonosulfate (PMS) systems have shown great potential in the treatment of antibiotic-containing wastewater. Herein, a Co–Ti-400 Fenton-like catalyst was synthesized by calcining Co-doped MIL-125(Ti) (Co–Ti) at 400 °C. Co–Ti-400 revealed an excellent catalytic performance for tetracycline hydrochloride (TCH) removal by activating PMS in a wide pH range (pH = 2–11). Significantly, 96.2% of TCH was removed in 1 hour over the catalyst (70 mg L−1 of TCH, 0.2 g L−1 of catalyst, 1 mM PMS, and pH = 4). Furthermore, Co–Ti-400 exhibited enhanced catalytic activity and stability in four cycles compared to the uncalcined sample (Co–Ti). Radicals (·OH, O2˙−, and SO4˙−) and 1O2 were proved to be the main active species during TCH degradation. Notably, Co–Ti-400/PMS showed good anti-interference towards inorganic salts in water. A reasonable degradation mechanism was proposed based on LC-MS analysis. With its exceptional catalytic performance and broad pH adaptability, Co–Ti-400 can be considered a potential catalyst for antibiotic removal. [ABSTRACT FROM AUTHOR]

Gold nanoparticles, or colloidal gold (AuNP), represent one of the most significant and established forms of sub-micron inorganic structures to be researched in recent years. AuNP physical and chemical properties are dictated by both their ligand surface chemistry and their size, which can be manipulated and tuned during their synthesis. In this study, aqueous linear and branched homo-polymers and (co)polymers are developed and used as surface stabilisers during AuNP synthesis. A library of such polymeric stabilisers were prepared using conventional free radical polymerisation techniques to incorporate units of varying AuNP surface binding affinity, using methacrylic acid (MAA) and oligo (ethylene glycol) methyl ether methacrylate (OEGMA) monomers and dodecane thiol (DDT) as the chain transfer agent. AuNPs were synthesised via HAuCl4·3H2O reduction in the presence of the prepared library of polymeric stabilisers. It was observed that variation of (co)polymer composition and architecture allowed for size-controlled gold nanoparticle synthesis, with AuNPs prepared ranging from 2.17 ± 0.07 nm to 4.83 ± 0.04 nm as determined by UV-vis spectroscopy. Varying (co)polymer composition and architecture also yielded variable catalytic behaviour in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH4, with catalytic reaction rates ranging from 1.0 s−1 to 45.3 s−1 and induction times ranging from 0 seconds to 2070 seconds depending on the polymeric stabilisers employed during synthesis. [ABSTRACT FROM AUTHOR]

The removal of harmful formaldehyde (HCHO) pollutants in indoor air is of great importance to protect human health. Herein, a flexible Pt/γ-Al2O3 (PAO) nanofiber membrane with a hierarchically porous structure was prepared by a one-step electrospinning method. The effects of Pt contents and calcination temperatures on the catalytic performance for HCHO oxidation at room temperature were investigated. The results indicate that Pt nanoparticles (NPs) are firmly decorated on the surface of γ-Al2O3 nanofibers since the loading of Pt NPs and the preparation of γ-Al2O3 nanofibers are conducted at the same time. PAO can oxidize HCHO to CO2 and H2O completely at room temperature. The catalytic activity of PAO first increases and then decreases with increasing Pt content or calcination temperature. The Pt content of 2 wt% and the calcination temperature of 700 °C are the optimal preparation parameters. The catalytic activity of PAO maintains good stability in 6 cycling tests after a simple regeneration heat treatment at 180 °C. The dioxymethylene, CO, carbonate and formate species are the main intermediates. The mechanism for HCHO oxidation was proposed as follows: HCHO + O2 → DOM and formate → carbonate species and CO → CO2. PAO also exhibits good flexibility and mechanical properties, good filtration performance for particulate matter and good fluid permeability. This work will shed a light on the design and fabrication of bifunctional catalytic materials for both HCHO and particulate matter removal in air purification. [ABSTRACT FROM AUTHOR]

The synthesis of a facile and efficient catalyst using Fe/Al supported on halloysite clay nanotubes (Fe–Al/HNT) for the selective oxidation of benzyl alcohol is reported here. The prepared catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The applicability of the prepared catalyst was studied for the oxidation of benzyl alcohol (BA) to benzaldehyde (BzA). The reaction conditions were optimized for high catalytic activity, stability and selectivity. The prepared catalyst showed good activity and stability for the solvent-free oxidation of benzyl alcohol. The catalyst was recycled for 5 times without losing its catalytic activity. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of twelve Rh(I) complexes with fluorinated NHC ligands are described. Seven molecular structures of these complexes were unequivocally elucidated by single crystal X-ray diffraction techniques. In all cases the metal center showed a distorted square planar geometry; including a chloride, a 1,5-cyclooctadiene and an NHC ligand coordinated to the Rh(I) center. Furthermore, the catalytic activity of the series of complexes was explored in the arylation of aldehydes, finding that the catalytic activity of the complexes is related to the number of fluorine atoms present on their structures, showing that as more fluorine atoms are found in the NHC ligand, the complexes become more active. This observation can be correlated with the fact that increasing the number of fluorine atoms in the NHC makes it a less electron-donating ligand, thus favoring the arylation of aldehydes. [ABSTRACT FROM AUTHOR]

A series of stable N-doped porous carbon encapsulated Ni nanoparticles (Ni@CN) were prepared via direct pyrolysis of Ni-MOF-74(N) and utilized for the catalytic transfer hydrogenation (CTH) of phenol to cyclohexanol with isopropanol as a hydrogen donor. The prepared catalysts were characterized by means of TG, XRD, BET, SEM, TEM and XPS. The effects of preparation and reaction conditions on the CTH performance were investigated. The results showed that the Ni particles of Ni@CN were smaller than that of Ni@C, which reflected that the doping of nitrogen could improve the dispersion of Ni nanoparticles. Moreover, electrons can be redistributed with N-doping. These two factors contribute to better catalytic activity. The Ni@CN-450 catalyst exhibited 99.3% phenol conversion with 100% cyclohexanol selectivity. Moreover, the catalysts could be recycled and reused easily with the help of a magnet and its catalytic performance did not decrease obviously even after five successive cycles. [ABSTRACT FROM AUTHOR]

Bimetallic core–shell nano-structured catalysis has sparked great interest due to the multiple possibilities relating to morphology, atomic arrangement, and composition. In the present study, three bimetallic core–shell-based nanocatalysts, viz. Pd(0)@enSiO2–TiO2–Ni, Pd(0)@enSiO2–Ni–TiO2, and Pd(0)@Ni–enSiO2–TiO2, were synthesized via an economical and facile method using Pd(0) and amine-functionalized silica–titania Ni(II) in the shell and core, respectively. The arrangement of Ni(II) was varied in the three nanocatalysts and their catalytic activities were studied for hydrogenation reactions. The best results were obtained in the case of Pd(0)@enSiO2–Ni–TiO2 among all the catalysts. The enhanced catalytic activity of Pd(0)@enSiO2–Ni–TiO2 was demonstrated via surface characterization techniques. Brunauer–Emmett–Teller (BET) analysis depicted the highest surface area in the case of Pd(0)@enSiO2–Ni–TiO2; X-ray photoelectron spectroscopy (XPS) analysis supported the results, as an additional peak from Ni(III) was observed in the spectrum of the reused catalyst, which suggested the presence of electronic interactions between Ni(II) in the core and Pd(0) in the shell. Moreover, Pd(0)@enSiO2–Ni–TiO2 was found to be highly active for carrying out hydrogenation reactions under mild reaction conditions with good yields and high selectivity, and it can be reused for up to five runs. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable electrocatalysts for oxygen reduction reaction (ORR) is a challenging task in energy conversion technologies. In this work, diverse axial ligands have been used to modify the ORR activity of transition metal and nitrogen codoped graphene (MN4-Gra). The weakening of the ORR intermediates by the axial ligand would activate these intermediates efficiently and improve the catalytic activity. Our study indicated that among the axial ligands adopted, nitrobenzene and benzene have good performance in improving the ORR activity. Several promising ORR catalysts are predicted. Among them, FeN4-Gra modified by nitrobenzene, i.e., FeN4-Gra/ben/NO2 has the best catalytic activity with a small overpotential of 0.21 V and energy barrier of 0.24 eV in the rate determining step, followed by RuN4-Gra/ben/NO2 and FeN4-Gra/benzene. These catalysts are also demonstrated to be stable by the calculated formation energies and dissolution potentials. The scaling relationships suggested that the adsorption energy of *OH and d band center would be good descriptors for predicting the highly efficient ORR catalysts. Therefore, axial ligand engineering would be a useful strategy to enhance the efficiency of ORR catalysts. [ABSTRACT FROM AUTHOR]

The development of ternary composites has gained great interest as they can be used as a catalyst in environmental remediation due to the transfer between different semiconductor nanoparticles because the difference in the band edge positions creates a potential gradient at the composite interface. Herein, for the first time, we reported a novel CuO@Ag@Bi2S3 ternary composite as a Z-scheme catalyst via homogeneous precipitation of Ag particles onto CuO and Bi2S3 by an ultrasonication method, wherein CuO nanoparticles were fabricated from the reduction of a Cu(II)–Schiff base complex. In the ternary composite, ∼10 nm Ag particles were uniformly dispersed on Bi2S3 and surrounded by CuO NPs, as demonstrated by TEM. Compared to the binary structures Ag@CuO, Ag@Bi2S3, and CuO@Bi2S3, the CuO@Ag@Bi2S3 ternary composite exhibits remarkably efficient catalytic activity for the removal of HIV drugs such as stavudine and zidovudine, and degradation of environmental pollutants (MB/RhB/MB + RhB, monocrotophos, and 4-nitrophenol). The framework of the formation of the composite, semiconductor behavior, high surface area, lowering of the electron–hole recombination, and the formation of a large number of ˙OH radicals are the crucial factors for the outstanding degradation of drugs and environmental pollutants by the CuO@Ag@Bi2S3 ternary composite through a Z-scheme mechanism. This work reveals that the CuO@Ag@Bi2S3 ternary composite is efficient at catalyzing not only the degradation of organic pollutants but also the removal of drugs, which might pave the way for its direct use in industry for environmental remediation. [ABSTRACT FROM AUTHOR]