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Carbon dioxide reduction through electrochemical energy is an emerging and appealing approach towards CO2 mitigation, and it is a potential technique in which the current and faradaic efficiencies can be optimized for the efficient/effective conversion of CO2 to solar fuel (storable high-density chemical energy). However, a challenge associated with the current state-of-the-art electrocatalytic systems is developing efficient, selective, and cost-effective heterogeneous catalysts. In this case, materials derived from metal–organic frameworks (MOFs) are promising electrocatalysts that not only possess porous structures similar to their parent MOFs but are also endowed with improved stability and conductivity, which are required in the CO2 reduction reaction (CO2RR). This review surveys the updated strategies to rationally design efficient MOF-based electrocatalysts and MOF-derived materials for CO2 reduction. Various MOF-derived materials are comprehensively discussed, together with the strategies aimed at improving product selectivity. Furthermore, active sites and detailed underlying mechanisms of CO2 reduction are discussed to gain better insights into the future development of electrocatalysts. This investigation aims to highlight the recent advances in the CO2RR to inspire the development of new techniques in designing electrocatalysts based on MOF structures with high performance and high stability. [ABSTRACT FROM AUTHOR]

Single-atom iron electrocatalysts have emerged as up-and-coming alternatives to platinum-based catalysts for the oxygen reduction reaction. However, their further development has been impeded by complex fabrication procedures and limitations in long-term stability. This study developed a chemical vapor deposition approach for synthesizing an efficient iron single-atom electrocatalyst denoted as Fe-SA@NC, utilizing vaporized ferrocene to deposit on a hierarchical N-doped carbon derived from ZIF-8. The preparation process maintained the initial pore structure throughout the deposition process by utilizing a two-step pyrolysis, preventing the collapse or deformation of the pore structure and frameworks. The optimized catalyst exhibited an exceptional half-wave potential (0.932 V) and kinetic current density (28.38 mA cm−2 at 0.9 V vs. RHE), along with high turnover frequency (36.37 s−1) and mass activity (5.68 A mg−1), and remarkable long-term stability in an alkaline electrolyte, exceeding those of commercial Pt/C and most previously reported iron-based electrocatalysts. Moreover, it also demonstrated outstanding practicability in both liquid and solid Zn–air batteries. The formation of well-dispersed Fe–N4 with strong interaction on hierarchical N-doped carbon was verified in the correlation of the structural activity and the excellent performance of Fe-SA@NC. This work sheds some light on the facile synthesis of single-atom catalysts with effective efficiency and stability. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have potential as drug carriers on the basis of their surface areas and pore volumes that allow for high drug loading and fast release. The present study investigated solvothermal synthesis and comprehensive characterization (BET, FTIR, PXRD and SEM) of two closely related series of microporous copper MOFs, Cu-MOF(s) (s = single linker) based on BPDC (biphenyl-4,4-dicarboxylate) linker and Cu-MOF(m) (m = mixed linker) comprising both BPDC and BPY (4,4-bipyridine) as linkers, for easy encapsulation and sustained delivery of two drugs, ibuprofen and montelukast sodium. Finally, one-way analysis of variance was applied for comparative evaluation between various concentration ratios (MOF : drug) to conclude statistically significant difference of encapsulation power and sustained release trend between the two Cu-MOFs using a UV-visible spectrophotometer by obtaining the absorbance value at λmax for each drug. Due to porous crystalline properties of our synthetized Cu-MOFs, we ensured excellent encapsulation and sustainability of both drugs to conceive a novel sustained release system for ibuprofen and montelukast sodium, which is more effective in comparison with conventional dosages of 2 to 3 times a day. [ABSTRACT FROM AUTHOR]

This study focuses on the mutual interaction of substituents in the nucleophile and substrate – cross interaction constant, ρXY, in the uncatalyzed aminolysis by substituting pyridine with phenyl carbonyl isothiocyanate. The mechanism was found to be a stepwise process with a rate-limiting breakdown of the –NCS leaving group. This stepwise reaction mechanism considers the cross-interaction constant (CIC) with rate-limiting breakdown of tetrahedral intermediate in gas and solvent phases. The corresponding Hammett coefficients are related to the substituents associated with (1) the nucleophiles (X), ρX (−1.93 to −6.54 for the gas phase and 10.5 to 18.9 in the solvent model), and with (2) the substituents associated with the phenyl ring of the substrate (Y), ρY (0.41–3.48 for the gas phase and 1.83 to −10.70 for the solvent model). It also includes the Brønsted coefficient with X, βX (0.11–1.52 for the gas phase and −2.57 to 3.96 for the solvent model), and CIC values, ρXY (0.69 for the gas phase and 0.87 for the solvent model). In this work, the NBO analysis, reaction potential, reaction electronic flux (REF), dual descriptor, and the structure-energy relationships were considered in interpreting the mechanistic criteria. [ABSTRACT FROM AUTHOR]

High-performing catalysts for the hydrogen evolution reaction (HER) via water electrolysis are of great importance for producing carbon-free green fuels. Compared to the routinely used metal-based systems under acidic conditions, metal-free pH-universal HER catalysts are smarter options taking into account the practical usability, sustainability, biocompatibility, and nominal cytotoxicity. Herein, we present an indigo-based organic conjugated porous polymer featuring a pronounced 2D few-layered morphology with surface-decorated hydrogen bonding sites for a deep catalyst–water contact and promising electrochemical HER activity. Indigo, being a vat dye, reduces in situ to its anionic leuco analogue and further promotes catalytic activity. The material manifested equipotent activity in acidic, alkaline, and neutral media superior to the contemporary metal-free carbonaceous electrocatalysts and comparable to the state-of-the-art metal-based catalytic systems. Under appropriate conditions, the material showed an overpotential of only 28 mV at 10 mA cm−2 current density. [ABSTRACT FROM AUTHOR]

Over the past decade, porous organic polymers (POPs) have emerged as powerful photocatalysts for organic transformations and wastewater decontamination. The surface properties and pore space of POPs have been tailored to find optimal physical dimensions for adsorption and catalysis, whereas playing with the donor–acceptor building units lends them unique prospects for bandgap engineering, beneficial for customized applications including the degradation of simple as well as persistent pollutants. Here in this critical perspective, we focused beyond these generic scenarios and provided a detailed physicochemical explanation for the experimental observations. Considering the invaluable role of excitons, along with mobile electrons and holes, we fundamentally justified the reactivities of POPs with regard to water treatment. Both semiconducting and molecular catalyst approaches have been considered for different types of POPs. Depending on the porosity, structural formation and defects in the POP backbone, the exciton formation, charge separation, charge diffusion, etc. are critically explained, highlighting the influence of the dielectric constant and skeletal polarizability of the material. The translation of this fundamental understanding to various reactive oxygen species generation through charge transfer (e.g., O2˙−) and exciton–exciton annihilation (e.g., 1O2) by proximity-induced FRET or Dexter pathways is discussed. The role of the hydrophilic POP skeleton in overall in-water photochemical applications is also discussed. Finally, the gaps in the current state-of-the-art are considered and the future prospects to mitigate these issues are argued. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) are not much investigated as catalysts in copolymer formation with cyclic esters. Herein, we report the ring-opening copolymerization of ε-caprolactone (CL) with δ-valerolactone (VL) using a recoverable and reusable Ti-metal based MOF, MIL-125 without any co-catalyst in a solvent-free medium. The synthesized copolymers are random in nature, exhibit lower crystallinity than those of the corresponding homo-polymers, and are totally free from metal contamination, which was established by a series of appropriate experiments and characterization techniques. [ABSTRACT FROM AUTHOR]

A systems chemistry approach is taken for compartmentalization of a continuous reaction medium (water and CO2) with induced creation of micro-heterogeneity in the medium by using a SOM (soft-oxometalate) catalyst. The first step involves compartmentalization of an assembled catalyst-photosensitizer duo catalysing the reduction of CO2 into formic acid in two reaction spaces: the interior of the compartment and the exterior of the compartment. The exterior compartment obeys typical surface activity driven nanocatalysis principles where the perturbation of the catalyst surface area inversely varies with product yield. The second step of disassembly to disrupt the SOM-catalyst, induced by addition of a base, releases the interior reaction product with total disappearance of the catalyst system. The assembly–disassembly cascade demonstrates the application of systems chemistry principles in perturbation, compartmentalization, catalysis and release of products with well-defined externally controlled stimuli such as concentration, light, and pH. The OSCR-catalyst reported here is an attempt to emulate Golgi bodies in the context of cellular chemistry on a functional level. [ABSTRACT FROM AUTHOR]

Visible light opto-electronic systems with synaptic characteristics have outstanding potential for a wide range of applications from photonic computing to the emulation of the basic functionalities of human visual systems. However, the complexities of photonic memristors and opto-synaptic devices are far beyond the concept of conventional image sensor technology. The development of artificial smart recognition systems requires an integrated complex network of image sensors and memory and processing units, which unfavorably consume a higher amount of electrical energy compared to their natural rival, i.e. the human visionary system. Here, we developed a single-unit photonic memristor for efficient visible light reception with non-volatile opto-resistive switching characteristics. The heterointerface engineering at the plasmonic unit based on heterostructured oxide films enabled the development of a visible-light tunable opto-synaptic device. The N2 incorporation into an atomically-thin In2O3 film at Au/In2O3–TiO2 heterointerfaces ensured the considerable decrease of opto-resistive switching current and enabled synergistic improvement of the long-term plasticity (LTP) of optical synapses. The relaxation time of opto-synapses was controlled by altering the polarization of the Au/In2O3 electrode, ensuring the synergistic improvement of LTP by the increase of photoconductance of the opto-synaptic device. The proof-of-concept of LTP for visible light plasmonic synapses can significantly simplify the circuitry of future artificial visionary systems and contribute to the outstanding development of neuro-optoelectronic technology. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) surface oxide films of post-transition liquid metals and their alloys have been recently introduced as an emerging category of ultra-thin functional semiconductor materials with fascinating physico-chemical and structural characteristics. These 2D films are natural surface oxide films of low melting temperature post-transition metals, similar to gallium, tin and their alloys. The natural 2D structure, accessibility and facile synthesis, in addition to their unique electronic characteristics, make this family of 2D materials a functional option for the development of a library of 2D materials and fabrication of 2D based semiconductor electronic and optoelectronic devices for novel applications. The present paper provides a comprehensive overview on the synthesis methods of 2D surface oxides of liquid metals and their families. The surface functionalization and post-processing approaches are also discussed and the potential applications of these 2D materials are reviewed. The recent findings have warranted the promising and ongoing development in the relevant fields and unprecedented growth of the number of functional devices based on these novel 2D materials. [ABSTRACT FROM AUTHOR]

A facile, single-step development strategy of a sub-nanoscopic Lewis acidic Co and basic imidazole grafted porous organic polymer is reported. The synergistic activation of an epoxide and CO2 by the Lewis pairs present in the material manifested their rapid conversion to cyclic carbonates under ambient pressure with high yield, selectivity, and TOF. [ABSTRACT FROM AUTHOR]

Highly water-soluble cyanocobalamin (also known as vitamin B12) is the most structurally macrocyclic complex comprising cobalt in the center of a corrin ring. Interestingly, it acts as a robust electrocatalyst in water oxidation at ∼0.58 V overpotential with a faradaic efficiency of 97.50% under neutral buffered conditions. The catalyst is impressively stable even after long-term bulk electrolysis, and homogeneous in nature, as established by a series of experiments and characterization techniques. [ABSTRACT FROM AUTHOR]

Tungsten oxide, as a typical functional transition metal oxide semiconductor, has been widely and intensively investigated for various applications. This review focuses on the recent progress of nanostructured tungsten oxide thin film devices, ranging from optoelectronics and ionics to iontronics. The recent research results on structural, defect, and ion intercalation aspects of tungsten oxide are first introduced in the review, as they are fundamental to the understanding and design of tungsten oxide devices. This part stresses the correlation between these aspects of tungsten oxide and its electronic structures. Then nanostructured tungsten oxide thin film devices are reviewed, especially photodetectors, electrochromic and supercapacitive devices, memristors and electrolyte-gated transistors. The figures of merit of the reported tungsten oxide photodetectors are comprehensively compared, analysed and summarised. New fabrication methods, novel configurations, multiple functions, and mechanism investigations of tungsten oxide electrochromic and supercapacitive devices are emphasized. In the exciting development of emerging iontronics, which bridges electronics and ionics, the operating mechanisms and performance of tungsten oxide-based memristors and electrolyte-gated transistors are underlined. The development trends, challenges, and opportunities of nanostructured tungsten oxide thin film devices are also analyzed and proposed. [ABSTRACT FROM AUTHOR]

Eight bidentate NHC/Ru complexes, namely [Ru]-1–[Ru]-8, were designed and prepared. In particular, [Ru]-2 displayed extraordinary performance even in open air for the dehydrogenative coupling of alcohols and hydroxides. Notably, an unprecedentedly low catalyst loading of 250 ppm and the highest TON of 32 800 and TOF of 3200 until now were obtained. [ABSTRACT FROM AUTHOR]

Dinuclear Co-based catalysts are used for the coupling reaction of epoxides and CO2 in the presence of a cocatalyst. The easily recyclable catalysts efficiently complete the coupling of CO2 with various epoxides into industrially important cyclic carbonates at low catalyst loading and displayed high catalytic activity under relatively low CO2 pressure and solvent-free conditions. The maximum TON (168 600) and TOF (3333 h−1) obtained in this work are the highest among the reported Co-complexes. [ABSTRACT FROM AUTHOR]

The spectrum of employment of ultra-thin layered materials in functional heterostructures and the precise control of their surface characteristics offer a remarkable platform to develop advanced optoelectronic devices. Herein, the wide bandgap and self-limiting surface oxides of Galinstan were innovatively employed as templates for the next sonochemical-assisted reactions to finally synthesize ultra-thin functionalized Ga2O3 nanosheets with tunable properties. To modulate the surface properties of the Ga2O3 nanosheets, various ionic solutions (aqueous AgNO3 and SeCl4) were used in the synthesis process. The decoration of the Ga2O3 nanosheets with Ag and Se nanostructures facilitated visible light responsivity of the Ga2O3 nanosheets. The functionalization of the gallium oxide nanosheets was also accompanied by unique rectifying behaviour of the Ga2O3 (Ag) based devices. The formation of either Schottky or Ohmic junctions between the Au electrode and Ga2O3 nanosheets and also the creation of type-II heterojunctions at the semiconductor heterointerfaces were the main controlling parameters of the optoelectronic devices. The implementation of the functionalized Ga2O3 nanosheets, as a complementary component of the optoelectronic device, enabled considerable improvement of the visible light responsivity in the TiO2–Ga2O3 films. Presenting both facile functionalization and controlling the properties of the nanosheets, this sonochemical technique can pave the way for further development of a new generation of ultra-thin materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

High-quality zeolite imidazole frameworks (ZIF-8, ZIF-67, and bimetallic Zn/Co-ZIF) were synthesized using the spray-drying technique and the mechanism of crystal growth during the whole process is discussed. It is also demonstrated that the crystallization mechanism for N-donor containing ditopic imidazolate (IM) ligands forming ZIF structures is divergent from MOF formation applying carboxylate ligands, and their formation using the spray dry method occurs via a unique mechanism. An intermediate amorphous phase was obtained after spray drying the feed solution, and the crystallographic ZIF structure was obtained during immersion in a solvent. Several characterization techniques, such as FTIR, XRD, SEM, porosity analysis, elemental analysis etc., were applied to examine the characteristic properties of materials, including, intermediate compounds and final products. The results proved that the spray drying procedure is a facile, continuous and effective synthetic route to produce MOFs (ZIFs) in higher quantities with high-quality properties such as high porosity, a large surface area, more active catalyst sites, etc. applying a minimum amount of time and energy which is unusual in common synthesis methods of MOFs. [ABSTRACT FROM AUTHOR]

While the role of negatively charged axial ligands (e.g. Cl−, Br− and I−) in tuning the reactivity and stability of molecular Ru water oxidation catalysts was well-documented, less was explored when axial ligands are neutral molecules. In this work, we reported the synthesis and full characterization of [Ru(NCNHCO)(bpy)L]+ complexes (L = DMSO, 1; L = 4-picoline, 2), where L is a neutral axial ligand. The effects of these axial ligands on the stability and reactivity of the catalysts were thoroughly investigated. Both complexes were competent to oxidize water with turnover numbers up to 463 and 107, respectively. Complex 1 initiated the water oxidation involving a PCET process. It was found that complex 2 afforded its corresponding Ru–aqua complex owing to the carboxylate dissociation, while complex 1 exhibited considerable stability in acidic aqueous solutions. On the other hand, in the presence of an oxidant, for complex 1 DMSO/H2O exchange occurred, facilitating water oxidation. In contrast, the Ru–O bond cleavage of complex 2 was inhibited, leading to an inferior catalytic performance. [ABSTRACT FROM AUTHOR]

The cyclization of carbon dioxide and propargylic alcohols, especially challenging substrates, were efficiently catalyzed by a green and recyclable AgI/OAc− system under atmospheric pressure, which is shown to be the most recyclable system with 20 recycle rounds and has the lowest loading among all the reported recyclable systems that work under atmospheric pressure. [ABSTRACT FROM AUTHOR]

A novel Zn/Co zeolitic imidazolate framework (ZIF) has been constructed by an easy and straightforward room temperature technique. Several characterization techniques such as SEM, TEM-EDX, single-crystal XRD and ICP have been applied to confirm that the structure formed is a sodalite (SOD) cage type structure. The Zn/Co-ZIF possesses a high nano-crystallinity and porosity with a large surface area. By tuning the amount of Co and Zn in the Zn/Co zeolitic imidazolate framework, the physical and chemical properties have been improved compared with those of the single metal frameworks (ZIF-8 and ZIF-67). Consequently, the Zn/Co-ZIF was investigated for two different applications; gas adsorption (CO2, CH4 and N2) and catalysis (CO2 conversion to cyclic carbonates) and the obtained results were compared with the performance of previously reported single metal frameworks (ZIF-8 and ZIF-67). Additionally, hydrolytic stability tests under ambient conditions and immersed in water at 75 °C were performed and pointed out that Zn/Co-ZIF exhibits a higher stability. Moreover, based on these results, the Zn/Co-ZIF demonstrates better properties compared with ZIF-8 and ZIF-67. [ABSTRACT FROM AUTHOR]

Lithium incorporation in metal–organic frameworks during solvothermal synthesis demonstrates a significant modification of the structure chemistry and surface properties of MOFs towards the adsorption selectivity of gas mixtures (CO2 and CH4) at ambient conditions. Variation of the lithium loading (xLi-MOF-5) led to tunability of the interpenetration resulting in materials with substantial differences in their properties. The behavior of xLi-MOF-5 was evaluated via phase identification based on XRD, functional group coordination using FTIR and adsorption measurements applying N2, CO2 and CH4 gas adsorption/desorption analysis. These efforts give rise to a new strategy to tailor MOFs for high efficiency CO2 adsorption and separation. [ABSTRACT FROM AUTHOR]

In this review, we have portrayed the structure, synthesis and applications of a variety of biomimetic MOFs from an unprecedented angle. Synthetic MOF analogues of five distinct enzymes: phosphotriesterase, hydrogenase, cytochrome P450, chymotrypsin and carbonic anhydrase, have been discussed with their skeletal comparison to actual enzymatic active sites as reference, and an explanation of catalytic pathways from the mechanistic cycle of the corresponding enzymes is depicted. We demonstrated critically each of the five discrete situations by assimilating available benchmark researches in an attempt to provide a concise literature source on the ingenious design strategies and versatile biomimetic applications of this domain of materials. [ABSTRACT FROM AUTHOR]

Zeolitic imidazole framework (ZIF)-67 is an efficient heterogeneous catalyst for the cycloaddition of carbon dioxide to epoxides to afford cyclic carbonates. In this work, ZIF-67 was synthesized by a simple and straightforward method at room temperature. The coupling reaction in the presence of ZIF-67 without any co-catalyst or solvent was studied under different conditions. The reaction conversion was more than 99% and the selectivity toward chloropropene carbonate was considerably higher (＞99%) than the previously reported ZIF-8. Moreover, the ZIF-67 catalyst could be recycled at least four times without noticeable loss of catalytic activity. [ABSTRACT FROM AUTHOR]

Novel catalytic materials are highly demanded to perform a variety of catalytic organic reactions. MOFs combine the benefits of heterogeneous catalysis like easy post reaction separation, catalyst reusability, high stability and homogeneous catalysis such as high efficiency, selectivity, controllability and mild reaction conditions. The possible organization of active centers like metallic nodes, organic linkers, and their chemical synthetic functionalization on the nanoscale shows potential to build up MOFs particularly modified for catalytic challenges. In this review, we have summarized the recent research progress in heterogeneous catalysis by MOFs and their catalytic behavior in various organic reactions, highlighting the key features of MOFs as catalysts based on the active sites in the framework. Examples of their post functionalization, inclusion of active guest species and metal nanoparticles have been discussed. Finally, the use of MOFs as catalysts for asymmetric heterogeneous catalysis and stability of MOFs has been presented as separate sections. [ABSTRACT FROM AUTHOR]

We report on the synthesis and characterization of second generation ruthenium indenylidene catalysts bearing unsymmetrical N-heterocyclic carbene (NHC) ligands denoted as RuCl2(3-phenyl-1-indenylidene)(1-mesityl-3-R-4,5-dihydroimidazol-2-ylidene)(PCy3), in which R is methyl 8a, octyl 8b or cyclohexyl 8c. The characterization of 8a–c was performed by NMR spectroscopy, elemental analysis, IR, HRMS and single-crystal X-ray diffraction analysis. In addition, the catalytic activity of the obtained initiators was evaluated in various representative metathesis reactions. The results reveal that the complexes 8a–c, bearing an N-alkyl side on the NHC, show a faster catalytic initiation than the reference complex 2. Complex 8a, which performs the best among the investigated indenylidene complexes, exhibits slower initiation but better overall efficiency than its benzylidene analogue 1c, especially in a low catalyst loading. [ABSTRACT FROM AUTHOR]

We report on the synthesis and characterization of the first generation of modified non-chelating indenylidene ruthenium catalysts denoted as RuCl2(4-methyl-3-(o-tolyl)-1-indenylidene)(PCy3)25a, RuCl2(3-(p-fluorophenyl)-1-indenylidene)(PCy3)25b, RuCl2(3-(2,6-xylyl)-1-indenylidene)(PCy3)25c and RuCl2(3-(1-naphthyl)-1-indenylidene)(PCy3)25d. The obtained complexes of 5a–d were characterized by means of NMR spectroscopy and elemental analysis. Moreover the structures of 5a–d were confirmed by single-crystal X-ray diffraction and compared with the standard ruthenium indenylidene complex 3 and the chelating benzylidene complex 2. Additionally, the catalytic performances of the obtained complexes 5a–d were evaluated in various metathesis reactions demonstrating that the ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions revealed a similar catalytic activity in comparison with the reference indenylidene catalyst 3. [ABSTRACT FROM AUTHOR]

New well-designed materials are highly demanded with the prospect of versatile properties, offering successful applications as alternates to conventional materials. Major new insights into metal-organic self-assembled structures assisting biochemical purposes have recently emerged. Metal-organic polyhedral cages are highlighted as new research materials to be used for therapeutic, sensing and imaging, purposes etc. This tutorial review covers achievements in the biochemical applications of these multinuclear complexes. Examples of their ability to aid the ionic transport, biomolecular sensing, imaging, and drug delivery are presented. [ABSTRACT FROM AUTHOR]