Unveiling Advancements: Trends and Hotspots of Metal-Organic Frameworks in Photocatalytic CO2 Reduction

Metal-organic frameworks (MOFs) are robust, crystalline, and porous materials featured by their superior CO2 adsorption capacity, tunable energy band structure, and enhanced photovoltaic conversion efficiency, making them highly promising for photocatalytic CO2 reduction reaction (PCO2RR). This study presents a comprehensive examination of the advancements in MOFs-based PCO2RR field spanning the period from 2011 to 2023. Employing bibliometric analysis, the paper scrutinizes the widely adopted terminology and citation patterns, elucidating trends in publication, leading research entities, and the thematic evolution within the field. The findings highlight a period of rapid expansion and increasing interdisciplinary integration, with extensive international and institutional collaboration. A notable emphasis on significant research clusters and key terminologies identified through co-occurrence network analysis, highlighting predominant research on MOFs such as UiO, MIL, ZIF, porphyrin-based MOFs, their composites, and the hybridization with photosensitizers and molecular catalysts. Furthermore, prospective design approaches for catalysts are explored, encompassing single-atom catalysts (SACs), interfacial interaction enhancement, novel MOF constructions, biocatalysis, etc. It also delves into potential avenues for scaling these materials from the laboratory to industrial applications, underlining the primary technical challenges that need to be overcome to facilitate the broader application and development of MOFs-based PCO2RR technologies.

Acceleration of Photoinduced Electron Transfer by Modulating Electronegativity of Substituents in Stable Zr-Metal-Organic Frameworks to Boost Photocatalytic CO2 Reduction

Photoreduction of CO2 with water into chemical feedstocks of fuels provides a green way to help solve both the energy crisis and carbon emission issues. Metal-organic frameworks (MOFs) show great potential for CO2 photoreduction. However, poor water stability and sluggish charge transfer could limit their application. Herein, three water-stable MOFs functionalized with electron-donating methyl groups and/or electron-withdrawing trifluoromethyl groups are obtained for the CO2 photoreduction. Compared with UiO-67-o-CF3-CH3 and UiO-67-o-(CF3)2, UiO-67-o-(CH3)2 achieves excellent performance with an average CO generation rate of 178.0 μmol g-1 h-1 without using any organic solvent or sacrificial reagent. The superior photocatalytic activity of UiO-67-o-(CH3)2 is attributed to the fact that compared with trifluoromethyl groups, methyl groups could not only elevate CO2 adsorption capacity and reduction potential but also promote photoinduced charge separation and migration. These are evidenced by gas physisorption, photoluminescence, time-resolved photoluminescence, electrochemical impedance spectroscopy, transient photocurrent characteristics, and density functional theory calculations. The possible working mechanisms of electron-donating methyl groups are also proposed. Moreover, UiO-67-o-(CH3)2 demonstrates excellent reusability for the CO2 reduction. Based on these results, it could be affirmed that the strategy of modulating substituent electronegativity could provide guidance for designing highly efficient photocatalysts.

Schottky Junction and D-A1 -A2 System Dual Regulation of Covalent Triazine Frameworks for Highly Efficient CO2 Photoreduction

Covalent triazine frameworks (CTFs) are emerging as a promising molecular platform for photocatalysis. Nevertheless, the construction of highly effective charge transfer pathways in CTFs for oriented delivery of photoexcited electrons to enhance photocatalytic performance remains highly challenging. Herein, a molecular engineering strategy is presented to achieve highly efficient charge separation and transport in both the lateral and vertical directions for solar-to-formate conversion. Specifically, a large π-delocalized and π-stacked Schottky junction (Ru-Th-CTF/RGO) that synergistically knits a rebuilt extended π-delocalized network of the D-A1 -A2 system (multiple donor or acceptor units, Ru-Th-CTF) with reduced graphene oxide (RGO) is developed. It is verified that the single-site Ru units in Ru-Th-CTF/RGO act as effective secondary electron acceptors in the lateral direction for multistage charge separation/transport. Simultaneously, the π-stacked and covalently bonded graphene is regarded as a hole extraction layer, accelerating the separation/transport of the photogenerated charges in the vertical direction over the Ru-Th-CTF/RGO Schottky junction with full use of photogenerated electrons for the reduction reaction. Thus, the obtained photocatalyst has an excellent CO2 -to-formate conversion rate (≈11050 µmol g-1 h-1 ) and selectivity (≈99%), producing a state-of-the-art catalyst for the heterogeneous conversion of CO2 to formate without an extra photosensitizer.

Modified UiO-66-Br Microphotocatalyst with High Electron Mobility Enhances Tetracycline Degradation

In this work, the Br functional group on the ligand UiO-66-Br was modified with a Bi-O bond through the secondary solvothermal method, and the synthesis method of visible light catalyst UB (UiO-66-BiOBr) with high electron mobility was explored. The findings indicate that the effective charge transfer of the functional group-modified material UB is 2.98 times and 1.22 times that of BiOBr and traditional UiO-66/BiOBr heterojunctions, respectively. Under simulated sunlight irradiation, the removal rate of tetracycline can reach 88.71%, and the photocatalytic performance is 22.73 times higher than that of UiO-66-Br. Moreover, it maintains good adsorption and photocatalytic performance under different laboratory and actual engineering water environment conditions. In the complex water environment of municipal wastewater, the degradation effect reaches more than 80%. Finally, the decomposition pathways of TC and ecotoxicities of the intermediates were analyzed via combining theoretical calculation, LC-MS/MS, and T.E.S.T.

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.

Constructing a metal-free 2D covalent organic framework for visible-light-driven photocatalytic reduction of CO2: a sustainable strategy for atmospheric CO2 utilization

A 2D polyimide-linked covalent organic framework (COF) with band gap energy of 2.2 eV is developed as a stable and efficient porous photocatalyst which shows CO2 reduction to formic acid, formaldehyde and methanol.

ZIF-8 metal organic framework composites as hydrogen evolution reaction photocatalyst: A review of the current state

In the past decade, extensive research has been devoted to synthesis of ZIF-8 materials for catalytic applications. As physico-chemical properties are synthesis-dependent, this review explores different synthesis strategies based the solvent and solvent-free synthesis of zeolitic imidazole framework. Accordingly, the effect of several parameters on the ZIF-8 synthesis were discussed including solvent, deprotonating agents, precursors ratio is delivered. Additionally, the advantages and disadvantages of each synthesis have been discussed and assessed. ZIF-8 textural and structural properties justify its wide use as a stable high surface area MOF in aqueous catalytic reactions. This review includes the applicatios of ZIF-8 materials in photocatalytic hydrogen evolution reaction (HER). The efficiency of the reviewed materials was fairly assessed. Finally, Limitations, drawbacks and future challenges were fully debated to ensure the industrial viability of the ZIFs.

Synthetic strategies for MOF-based single-atom catalysts for photo- and electro-catalytic CO2 reduction

The excessive CO₂ emission has resulted in climate changes, which has threatened human existence. Photocatalytic and electrocatalytic CO₂ reduction, driven by wind electricity and solar energy, are feasible ways of tackling carbon dioxide emission, as both energies are clean and renewable. Single-atom catalyst (SAC) is a candidate owing to excellent electrocatalytic and photocatalytic performance. Methods for preparing an SAC by using metal-organic frameworks (MOFs) as support or precursors are summarized. Also, applications in energy conversion are exhibited. However, the real challenge is to improve the selectivity of catalytic reactions to yield higher value products, which is to be discussed.

Metal-organic frameworks and their composites for fuel and chemical production via CO2 conversion and water splitting

Increase in the global energy demand has been leading to major energy crises in recent years. The use of excess fossil fuels for energy production is causing severe global warming, as well as energy shortage. To overcome the global energy crisis, the design of various chemical structures as efficient models for the generation of renewable energy fuels is very much crucial, and will limit the use of fossil fuels. Current challenges involve the design of Metal-Organic Framework (MOF) materials for this purpose to diminish the energy shortage. The large surface area, tunable pore environment, unique structural property and semiconducting nature of the highly porous MOF materials enhance their potential applications towards the production of enhanced energy fuels. This review is focused on the architecture of MOFs and their composites for fuels and essential chemicals production like hydrogen, methane, ethanol, methanol, acetic acid, and carbon monoxide, which can be used as renewable fuel energy sources to limit the use of fossil fuels, thereby reducing global warming.

Rhodium-Based Metal-Organic Polyhedra Assemblies for Selective CO2 Photoreduction

Heterogenization of molecular catalysts via their immobilization within extended structures often results in a lowering of their catalytic properties due to a change in their coordination sphere. Metal-organic polyhedra (MOP) are an emerging class of well-defined hybrid compounds with a high number of accessible metal sites organized around an inner cavity, making them appealing candidates for catalytic applications. Here, we demonstrate a design strategy that enhances the catalytic properties of dirhodium paddlewheels heterogenized within MOP (Rh-MOP) and their three-dimensional assembled supramolecular structures, which proved to be very efficient catalysts for the selective photochemical reduction of carbon dioxide to formic acid. Surprisingly, the catalytic activity per Rh atom is higher in the supramolecular structures than in its molecular sub-unit Rh-MOP or in the Rh-metal-organic framework (Rh-MOF) and yields turnover frequencies of up to 60 h^-1 and production rates of approx. 76 mmole formic acid per gram of the catalyst per hour, unprecedented in heterogeneous photocatalysis. The enhanced catalytic activity is investigated by X-ray photoelectron spectroscopy and electrochemical characterization, showing that self-assembly into supramolecular polymers increases the electron density on the active site, making the overall reaction thermodynamically more favorable. The catalyst can be recycled without loss of activity and with no change of its molecular structure as shown by pair distribution function analysis. These results demonstrate the high potential of MOP as catalysts for the photoreduction of CO₂ and open a new perspective for the electronic design of discrete molecular architectures with accessible metal sites for the production of solar fuels.

Challenges and prospects in the selective photoreduction of CO2 to C1 and C2 products with nanostructured materials: a review

Solar fuel generation through CO₂ hydrogenation is the ultimate strategy to produce sustainable energy sources and alleviate global warming. The photocatalytic CO₂ conversion process resembles natural photosynthesis, which regulates the ecological systems of the earth. Currently, most of the work in this field has been focused on boosting efficiency rather than controlling the distribution of products. The structural architecture of the semiconductor photocatalyst, CO₂ photoreduction process, product analysis, and elucidating the CO₂ photoreduction mechanism are the key features of the photoreduction of CO₂ to generate C1 and C2 based hydrocarbon fuels. The selectivity of C1 and C2 products during the photocatalytic CO₂ reduction have been ameliorated by suitable photocatalyst design, co-catalyst, defect states, and the impacts of the surface polarisation state, etc. Monitoring product selectivity allows the establishment of an appropriate strategy to generate a more reduced state of a hydrocarbon, such as CH₄ or higher carbon (C2) products. This article concentrates on studies that demonstrate the production of C1 and C2 products during CO₂ photoreduction using H₂O or H₂ as an electron and proton source. Finally, it highlights unresolved difficulties in achieving high selectivity and photoconversion efficiency of CO₂ in C1 and C2 products over various nanostructured materials.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.

Post-synthetic modifications (PSM) on metal-organic frameworks (MOFs) for visible-light-initiated photocatalysis

The utilization of green and sustainable solar energy via photocatalysis is regarded as a promising strategy to tackle the ever-increasing energy shortage and environmental deterioration. In addition to traditional semiconductor-based photocatalysts, metal-organic frameworks (MOFs), a class of crystalline micro-mesoporous hybrid materials constructed from metal or metal nodes interconnected with multi-dentate organic linkers, are emerging as a new type of photocatalytic material. Post-synthetic modifications (PSM) on MOFs, in which chemical transformations or exchanges are made on pre-synthesized MOF materials, are found to be a powerful strategy for fabricating photoactive MOFs based on already existing MOFs. In this frontier article, different PSM strategies for the development of photoactive MOFs, including coordination on unsaturated metal sites, metalation on open coordinated sites, covalent modifications on ligands, ligand exchange, metal exchange and cavity encapsulation, have been summarized. Our views on the challenges and the direction in developing photocatalytic MOFs by PSM are also addressed. We hope that this frontier article can provide some guidance for rational designing of highly efficient MOF-based photocatalysts via PSM strategies and to stimulate more research interest to be devoted to this promising yet largely unexplored field.

Metal-Organic Frameworks: Molecules or Semiconductors in Photocatalysis?

In the realm of solids, metal-organic frameworks (MOFs) offer unique possibilities for the rational engineering of tailored physical properties. These derive from the modular, molecular make-up of MOFs, which allows for the selection and modification of the organic and inorganic building units that construct them. The adaptable properties make MOFs interesting materials for photocatalysis, an area of increasing significance. But the molecular and porous nature of MOFs leaves the field, in some areas, juxtapositioned between semiconductor physics and homogeneous photocatalysis. While descriptors from both fields are applied in tandem, the gap between theory and experiment has widened in some areas, and arguably needs fixing. Here we review where MOFs have been shown to be similar to conventional semiconductors in photocatalysis, and where they have been shown to be more like infinite molecules in solution. We do this from the perspective of band theory, which in the context of photocatalysis, covers both the molecular and nonmolecular principles of relevance.

Trends and Prospects in UiO-66 Metal-Organic Framework for CO2 Capture, Separation, and Conversion

Among thousands of known metal-organic frameworks (MOFs), the University of Oslo's MOF (UiO-66) exhibits unique structure topology, chemical and thermal stability, and intriguing tunable properties, that have gained incredible research interest. This paper summarizes the structural advancement of UiO-66 and its role in CO₂ capture, separation, and transformation into chemicals. The first part of the review summarizes the fast-growing literature related to the CO₂ capture reported by UiO-66 during the past ten years. The second part provides an overview of various advancements in UiO-66 membranes in CO₂ purification. The third part describes the role of UiO-66 and its composites as catalysts for CO₂ conversion into useful products. Despite many achievements, significant challenges associated with UiO-66 are addressed, and future perspectives are comprehensively presented to forecast how UiO-66 might be used further for CO₂ management.

An Anthracene-Based Metal-Organic Framework for Selective Photo-Reduction of Carbon Dioxide to Formic Acid Coupled with Water Oxidation

A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h^-1 in addition to oxygen, which was produced with a TOF of 0.54 h^-1 . No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here.

Critical Aspects of Metal-Organic Framework-Based Materials for Solar-Driven CO2 Reduction into Valuable Fuels

Photoreduction of CO2 into value-added fuels is one of the most promising strategies for tackling the energy crisis and mitigating the "greenhouse effect." Recently, metal-organic frameworks (MOFs) have been widely investigated in the field of CO2 photoreduction owing to their high CO2 uptake and adjustable functional groups. The fundamental factors and state-of-the-art advancements in MOFs for photocatalytic CO2 reduction are summarized from the critical perspectives of light absorption, carrier dynamics, adsorption/activation, and reaction on the surface of photocatalysts, which are the three main critical aspects for CO2 photoreduction and determine the overall photocatalytic efficiency. In view of the merits of porous materials, recent progress of three other types of porous materials are also briefly summarized, namely zeolite-based, covalent-organic frameworks based (COFs-based), and porous semiconductor or organic polymer based photocatalysts. The remarkable performance of these porous materials for solar-driven CO2 reduction systems is highlighted. Finally, challenges and opportunities of porous materials for photocatalytic CO2 reduction are presented, aiming to provide a new viewpoint for improving the overall photocatalytic CO2 reduction efficiency with porous materials.

A review of the research status of CO2 photocatalytic conversion technology based on bibliometrics

In order to clarify the research status, hot spots and development trend in the field of conversion of carbon dioxide, a large amount of literature data set in the scientific network database was analyzed by bibliometrics.

Integrated nano-architectured photocatalysts for photochemical CO2 reduction

Recent advances in nanotechnology, especially the development of integrated nanostructured materials, have offered unprecedented opportunities for photocatalytic CO2 reduction. Compared to bulk semiconductor photocatalysts, most of these nanostructured photocatalysts offer at least one advantage in areas such as photogenerated carrier kinetics, light absorption, and active surface area, supporting improved photochemical reaction efficiencies. In this review, we briefly cover the cutting-edge research activities in the area of integrated nanostructured catalysts for photochemical CO2 reduction, including aqueous and gas-phase reactions. Primarily explored are the basic principles of tailor-made nanostructured composite photocatalysts and how nanostructuring influences photochemical performance. Specifically, we summarize the recent developments related to integrated nanostructured materials for photocatalytic CO2 reduction, mainly in the following five categories: carbon-based nano-architectures, metal-organic frameworks, covalent-organic frameworks, conjugated porous polymers, and layered double hydroxide-based inorganic hybrids. Besides the technical aspects of nanostructure-enhanced catalytic performance in photochemical CO2 reduction, some future research trends and promising strategies are addressed.

Metal-Organic Frameworks as a Platform for CO2 Capture and Chemical Processes: Adsorption, Membrane Separation, Catalytic-Conversion, and Electrochemical Reduction of CO2

The continuous rise in the atmospheric concentration of carbon dioxide gas (CO2) is of significant global concern. Several methodologies and technologies are proposed and applied by the industries to mitigate the emissions of CO2 into the atmosphere. This review article offers a large number of studies that aim to capture, convert, or reduce CO2 by using a superb porous class of materials (metal-organic frameworks, MOFs), aiming to tackle this worldwide issue. MOFs possess several remarkable features ranging from high surface area and porosity to functionality and morphology. As a result of these unique features, MOFs were selected as the main class of porous material in this review article. MOFs act as an ideal candidate for the CO2 capture process. The main approaches for capturing CO2 are pre-combustion capture, post-combustion capture, and oxy-fuel combustion capture. The applications of MOFs in the carbon capture processes were extensively overviewed. In addition, the applications of MOFs in the adsorption, membrane separation, catalytic conversion, and electrochemical reduction processes of CO2 were also studied in order to provide new practical and efficient techniques for CO2 mitigation.

Hierarchically macro-meso-microporous metal-organic framework for photocatalytic oxidation

The macro-meso-microporous and defective metal-organic framework constructed by transition metal Zn and 2,2'-bipyridine-5,5'-carboxylate was synthesized in CO2-expanded solvent. It shows high photocatalytic activity and selectivity for the oxidation of amines to imines under mild conditions, i.e., air as an oxidant, room temperature, and involving no photosensitizer or cocatalyst.

Co-immobilization of a Rh Catalyst and a Keggin Polyoxometalate in the UiO-67 Zr-Based Metal-Organic Framework: In Depth Structural Characterization and Photocatalytic Properties for CO2 Reduction

The Keggin-type polyoxometalate (POM) PW₁₂O₄₀^3- and the catalytic complex Cp*Rh(bpydc)Cl₂ (bpydc = 2,2'-bipyridine-5,5'-dicarboxylic acid) were coimmobilized in the Zr(IV) based metal organic framework UiO-67. The POM is encapsulated within the cavities of the MOF by in situ synthesis, and then, the Rh catalytic complex is introduced by postsynthetic linker exchange. Infrared and Raman spectroscopies, ³¹P and ¹³C MAS NMR, N₂ adsorption isotherms, and X-ray diffraction indicate the structural integrity of all components (POM, Rh-complex and MOF) within the composite of interest (PW₁₂,Cp*Rh)@UiO-67. DFT calculations identified two possible locations of the POM in the octahedral cavities of the MOF: one at the center of a UiO-67 pore with the Cp*Rh complex pointing toward an empty pore and one off-centered with the Cp*Rh pointing toward the POM. ³¹P-¹H heteronuclear (HETCOR) experiments ascertained the two environments of the POM, equally distributed, with the POM in interaction either with the Cp* fragment or with the organic linker. In addition, Pair Distribution Function (PDF) data were collected on the POM@MOF composite and provided key evidence of the structural integrity of the POM once immobilized into the MOF. The photocatalytic activity of the (PW₁₂,Cp*Rh)@UiO-67 composite for CO₂ reduction into formate and hydrogen were evaluated. The formate production was doubled when compared with that observed with the POM-free Cp*Rh@UiO-67 catalyst and reached TONs as high as 175 when prepared as thin films, showing the beneficial influence of the POM. Finally, the stability of the composite was assessed by means of recyclability tests. The combination of XRD, IR, ICP, and PDF experiments was essential in confirming the integrity of the POM, the catalyst, and the MOF after catalysis.

The role of leached Zr in the photocatalytic reduction of CO2 to formate by derivatives of UiO-66 metal organic frameworks

Photoreduction of CO₂ to formate by UiO-66 Zr MOF derivatives is explained by Zr leaching.

Frustrated Lewis pair-mediated fixation of CO2 within a metal-organic framework

Finding pragmatic solutions to curb the accumulation of atmospheric CO2 and tackle the associated greenhouse effect is challenging. Herein, we demonstrate the use of an in situ formed frustrated Lewis pair (FLP) within a metal-organic framework (MOF) to effectively hydrogenate CO2 to methoxide at a relatively low temperature and pressure. The work presents a step toward the discovery of practical catalysts for CO2 reduction and conversion.

Recent Advances in MOF-based Nanocatalysts for Photo-Promoted CO2 Reduction Applications

The conversion of CO2 to valuable substances (methane, methanol, formic acid, etc.) by photocatalytic reduction has important significance for both the sustainable energy supply and clean environment technologies. This review systematically summarized recent progress in this field and pointed out the current challenges of photocatalytic CO2 reduction while using metal-organic frameworks (MOFs)-based materials. Firstly, we described the unique advantages of MOFs based materials for photocatalytic reduction of CO2 and its capacity to solve the existing problems. Subsequently, the latest research progress in photocatalytic CO2 reduction has been documented in detail. The catalytic reaction process, conversion efficiency, as well as the product selectivity of photocatalytic CO2 reduction while using MOFs based materials are thoroughly discussed. Specifically, in this review paper, we provide the catalytic mechanism of CO2 reduction with the aid of electronic structure investigations. Finally, the future development trend and prospect of photocatalytic CO2 reduction are anticipated.

Anchoring CoII Ions into a Thiol-Laced Metal-Organic Framework for Efficient Visible-Light-Driven Conversion of CO2 into CO

Using solar energy to convert CO₂ into valuable fuels or chemicals offers a powerful solution to urgent energy and environmental problems. However, the development of efficient and selective catalysts remains a considerable scientific challenge. To address this, catalytically active Co^II centers can be anchored into the porous matrix of metal-organic frameworks (MOFs) by utilizing a robust Zr-based MOF (Zr-DMBD) functionalized with freestanding thiol groups to enable efficient post-synthetic metal insertion. The thus-prepared Zr-DMBD-Co MOF solids are modified by well-defined Co-thiolate units and have the capability of photocatalytically converting CO₂ into CO with high efficiency and selectivity under visible-light irradiation in a water-containing system. The turnover number and CO selectivity reach as high as 97 941 and 98 %, respectively.

Carbon capture and conversion using metal–organic frameworks and MOF-based materials

This review summarizes recent advances and highlights the structure–property relationship on metal–organic framework-based materials for carbon dioxide capture and conversion.

A local hydrophobic environment in a metal–organic framework for boosting photocatalytic CO2 reduction in the presence of water

The methylene groups surrounding the metal center in a metal–organic framework provide hydrophobic repulsive forces to H₂O, resulting in a high catalytic activity (TOF = 73.8 h⁻¹, selectivity of 96%) for photodriven CO₂ reduction into CO.

Metal-Organic-Framework-Derived Co3 S4 Hollow Nanoboxes for the Selective Reduction of Nitroarenes

MOF-derived Co₃ S₄ /CN hollow nanoboxes (CN=nitrogen-doped carbon) was used to catalyze the chemoselective reduction of nitroarenes to anilines under mild reaction conditions with H₂ as the reducing agent. The catalyst provides high conversion efficiencies and selectivities for a variety of nitroarene substrates that contain electron-donating or electron-withdrawing substituents under mild reaction conditions (in methanol at 60 °C). Further, the nanobox inhibits both dehalogenation and vinyl hydrogenation reactions, which are common limitations of state-of-the-art Pd-based catalysts. Because the reactions result in pure aniline products, the need for separation by column chromatography is eliminated. The resulting anilines are easily separated from the methanolic reaction solution in just three simple steps (centrifugation, decantation, and drying). If employed in industrial processes, catalysts of this kind would significantly reduce the amount of waste organic solvent generated and thus satisfy the need for sustainable chemical processes.

Pristine Metal-Organic Frameworks and their Composites for Energy Storage and Conversion

Metal-organic frameworks (MOFs), a new class of crystalline porous organic-inorganic hybrid materials, have recently attracted increasing interest in the field of energy storage and conversion. Herein, recent progress of MOFs and MOF composites for energy storage and conversion applications, including photochemical and electrochemical fuel production (hydrogen production and CO₂ reduction), water oxidation, supercapacitors, and Li-based batteries (Li-ion, Li-S, and Li-O₂ batteries), is summarized. Typical development strategies (e.g., incorporation of active components, design of smart morphologies, and judicious selection of organic linkers and metal nodes) of MOFs and MOF composites for particular energy storage and conversion applications are highlighted. A broad overview of recent progress is provided, which will hopefully promote the future development of MOFs and MOF composites for advanced energy storage and conversion applications.

Metal-Organic-Framework-Based Catalysts for Photoreduction of CO2

Photoreduction of CO₂ into reusable carbon forms is considered as a promising approach to address the crisis of energy from fossil fuels and reduce excessive CO₂ emission. Recently, metal-organic frameworks (MOFs) have attracted much attention as CO₂ photoreduction-related catalysts, owing to their unique electronic band structures, excellent CO₂ adsorption capacities, and tailorable light-absorption abilities. Recent advances on the design, synthesis, and CO₂ reduction applications of MOF-based photocatalysts are discussed here, beginning with the introduction of the characteristics of high-efficiency photocatalysts and structural advantages of MOFs. The roles of MOFs in CO₂ photoreduction systems as photocatalysts, photocatalytic hosts, and cocatalysts are analyzed. Detailed discussions focus on two constituents of pure MOFs (metal clusters such as Ti-O, Zr-O, and Fe-O clusters and functional organic linkers such as amino-modified, photosensitizer-functionalized, and electron-rich conjugated linkers) and three types of MOF-based composites (metal-MOF, semiconductor-MOF, and photosensitizer-MOF composites). The constituents, CO₂ adsorption capacities, absorption edges, and photocatalytic activities of these photocatalysts are highlighted to provide fundamental guidance to rational design of efficient MOF-based photocatalyst materials for CO₂ reduction. A perspective of future research directions, critical challenges to be met, and potential solutions in this research field concludes the discussion.