Hierarchically Porous Metal-Organic Framework/MoS2 Interface for Selective Photocatalytic Conversion of CO2 with H2 O into CH3 COOH

Synergistic Enhancement of Ligand & Cluster Connectivity to Construct Highly Stable Fluorescein-Based MOFs with Thickened Channel Walls for Boosting Photocatalytic Activity

Fabricating visible-light-responsive metal-organic frameworks (MOFs) with high stability and effective catalytic functionality remains a long-term pursuit yet a great challenge. Herein, a strategy of increasing ligand and cluster connectivity is developed to construct highly stable fluorescein MOFs, La-CFL, presenting a new (4,8)-connected topological structure compared to Cd-FL constructed using 6-connected dinuclear clusters and 3-connected tritopic ligands. La8(CFL)4 containers like Chinese "Ritual Wine Vessels (Jue)" resemble linear arrangements interconnected by the [La2(COO)4] clusters. This arrangement induces benzene rings and xanthene rings to locate on the inner walls of 1D channels, resulting in thicker channel walls that contribute to enhanced stability. Consequently, La-CFL demonstrates outstanding catalytic performance in thiol-ene reactions under green LED irradiation. It exhibits 2.3 times higher efficiency than Cd-FL while reducing reaction time to one-fifth at 20 min. Furthermore, La-CFL displays size-selective catalysis and retains full activity for 20 cycles without degradation, an improvement over Cd-FL's recyclability limitations.

Facts and Fictions About Photocatalytic CO2 Reduction to C2+ Products

In response to carbon neutrality, photocatalytic reduction of CO2 has been the subject of growing interest for researchers over the past few years. Multi-carbon products (C2+) with higher energy density and larger market value produced from photocatalytic reduction of CO2 are still very limited owing to the low photocatalytic productivity and poor selectivity of products. This review focuses on the recent progress on photocatalytic reduction of CO2 towards C2+ products from the perspective of performance evaluation and mechanistic understanding. We first provide a systematic description of the entire fundamental procedures of photocatalytic reduction of CO2. An in-depth strategy analysis for improving the selectivity of photocatalytic reduction of CO2 to C2+ products is then addressed. Then the focus was on summarizing the ways to improve C2+ selectivity. The intrinsic mechanisms of photocatalytic reduction of CO2 to C2+ products are summarized in the final. Combining the foundation of photocatalysis with promising catalyst strategies, this review will offer valuable guidance for the development of efficient photocatalytic systems for the synthesis of C2+ products.

Crystal-Facet Engineering of Mesoporous CuS Cascade Nanoreactors Enhances Photocatalytic C-C Coupling of CO2-to-C2H4

Crystal-facet heterojunction engineering of mesoporous nanoreactors with highly redox-active represents an efficacious strategy for the transformation of CO2 into valuable C2 products (e.g., C2H4). Herein, hollow mesoporous cube-like CuS nanoreactors (~860 nm) with controlled anisotropic crystal-facets are prepared through an interfacial-confined ion dynamic migration-rearrangement strategy. The regulation of the S2- ion concentration facilitates the modulation of the highly active (110) to (100) crystal-facet ratios from 0.119 to 0.288, and induces the formation of anisotropic crystal-facet heterojunctions. The controllable crystal-facet heterojunctions trigger the directional charge carrier migration, and are accompanied with the formation of tandem S-defect sites (Cu0-S1@S3). Both of them promote the efficient electron-hole pair dissociation and attain asymmetric C-C coupling. The hollow mesoporous CuS nanoreactors with optimized crystal-facet ratio of 0.224 (HMe-CuS-3) deliver a high selectivity of 72.7 % for the photocatalytic reduction of CO2 to acetylene (C2H2). Further constructed Au-(110) and Co3O4-(100) spatially separated cascade nanoreactors (SS-Au@Co3O4-CuS) achieve CO2-C2H4 photoreduction, in which the Co-sites enhance H2O dissociation to provide protons and the protonation of *CO to *COH. The *COH is further captured by Au-sites to accomplish the asymmetric *CO-*COH coupling and subsequent protonation, ensuring a high C2H4 generation rate of 4.11 μmol/g/h with a selectivity as high as 90.6 %.

In-Situ Growth of Metallocluster Inside Heterometal-Organic Cage to Switch Electron Transfer for Targeted CO2 Photoreduction

Construction of metal-organic cages (MOCs) with internal modifications is a promising avenue to build enzyme-like cavities and unlocking the mystery of highly catalytic activity and selectivity of enzymes. However, current interests are mainly focused on single-metal-node cages, little achievement has been expended to metallocluster-based architectures, and the in situ endogenous generation of metal clusters. Herein, based on the hard-soft-acids-bases (HSAB), the metallocluster-based heterometallic MOC (Cu3VMOP) constructed of [Cu3OPz3]+ and [V6O6(OCH3)9(SO4)(CO2)3]2- clusters was obtained by one-pot method. In addition, Cu4I4 was generated in situ in the cage to form Cu4I4@Cu3VMOP by the coordination-driven hierarchical self-assembly strategy. As catalysts for CO2 reduction, Cu3VMOP produces HCOOH and CH3COOH as the main reduction product with yield of CH3COOH up to 0.9 mmol g-1, ranking among the highest value of reported materials, whereas Cu4I4@Cu3VMOP exhibited targeted CO2-to-HCOOH conversion with 100 % formic acid selectivity and the yield outperforms that of Cu3VMOP by 5 fold. Theoretical calculations and femtosecond time-resolved transient absorption reveal that endogenous Cu4I4 not only regulates orbital arrangements and enhances localized electron states to generate a long-lived charge-separated state, but also raises *CO coupling energy barrier, resulting in the targeted conversion of CO2 to formic acid.

Collective Effect in Hierarchical Porous MOFs Combining Single Atoms and Nanoparticles for Enhanced CO2 Photoreduction to CO

Reasonable construction of atomically accurate photocatalysts is the key to building efficient photocatalytic systems. Herein, we propose a collective effects strategy that enables the consolidation of both cobalt single atoms (CoSAs) and nickel nanoparticles (NiNPs) in hierarchical porous MOFs for the foundational features for the preparation of high-performance photocatalysts. Among them, the optimal sample CoSAs/Al-bpydc/NiNPs achieved a CO generation rate of 12.8 mmol·g-1·h-1 and selectivity of 91% in 4 h. According to the experiment characterizations and theoretical simulations, we found that CoSAs facilitate CO2 adsorption and activation, while NiNPs promote hydrogen spillover and transfer of hydrogen protons to CoSAs, highlighting the collective effect of the catalytic system with multiple active sites. Most importantly, as a proof of concept, this performance enhancement strategy can also be applied to other hierarchically porous MOF photocatalysts, such as Al-bpdc, DUT-4, and UiO-67. This work provides new insight into the development of performance optimization of CO2 conversion photocatalysts through the ingenious design of collective catalytic sites.

Reticular Materials for Photocatalysis

Photocatalysis leverages solar energy to overcome the thermodynamic barrier, enabling efficient chemical reactions under mild conditions. It can greatly reduce reliance on traditional energy sources and has attracted significant research interest. Reticular materials, including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), represent a class of crystalline materials constructed from molecular building blocks linked by coordination and covalent bonds, respectively. Reticular materials function as heterogeneous catalysts, combining well-defined structures and high tailorability akin to homogeneous catalysts. In this review, the regulation of light absorption, charge separation, and surface reactions in the photocatalytic process through precise molecular-level design based on the features of reticular materials is elaborated. Notably, for MOFsmicroenvironment modulation around catalytic sites affects photocatalytic performance is delved, with emphasis on their unique dynamic and flexible microenvironments. For COFs, the inherent excitonic effects due to their fully organic nature is discussed and highlight the strategies to regulate excitonic effects for charge- and/or energy-transfer-mediated photocatalysis. Finally, the current challenges and future directions in this field, aiming to provide a comprehensive understanding of how reticular materials can be optimized for enhanced photocatalysis is discussed.

Bioinspired catalytic pocket promotes CO2-to-ethanol photoconversion on colloidal quantum wells

Sluggish surface reaction is a critical factor that strongly governs the efficiency of photocatalytic solar fuel production, particularly in CO2-to-ethanol photoconversion. Here, inspired by the principles underlying enzyme catalytic proficiency and specificity, we report a biomimetic photocatalyst that affords superior CO2-to-ethanol photoreduction efficiency (5.5 millimoles gram-1 hour-1 in average with 98.2% selectivity) distinctly surpassing the state of the art. The key is to create a class of catalytic pocket, which contains spatially organized NH2…Cu-Se(-Zn) multiple functionalities at close range, over ZnSe colloidal quantum wells. Such structure offers a platform to mimic the concerted cooperation between the active site and surrounding secondary/outer coordination spheres in enzyme catalysis. This is manifested by the chemical adsorption and activation of CO2 via a bent geometry, favorable stabilization toward a variety of important intermediates, promotion of multielectron/proton transfer processes, etc. These results highlight the potential of incorporating enzyme-like features into the design of photocatalysts to overcome the challenges in CO2 reduction.

CO-Free Aminocarbonylation of Terminal Alkynes Catalyzed by Synergistic Effect From Metal-Organic Frameworks

Incorporation of CO into substrates to construct high-value carbonyl compounds is an intensive industrial carbonylation procedure, however, high toxicity and wide explosion limits (12.5-74.0 vol% in air) of CO limit its application in industrial production. The development of a CO-free catalytic system for carbonylation is one of ideal methods, but full of challenge. Herein, this study reports the CO-free aminocarbonylation conversion of terminal alkynes synergistically catalyzed by a unique Co(ІІ)/Ag(І) metal-organic framework (MOF), in which the combination of isocyanides and O2 is employed as safe and green source of aminocarbonyl. This reaction has broad substrate applicability in terminal alkyne and isocyanides components with 100% atom economy. The bimetal MOF catalyst can be recycled at least five times without substantial loss of catalytic activities. Mechanistic investigations demonstrate that the synergistic effect between Ag(I) and Co(II) sites can efficiently activate terminal alkyne and isocyanides, respectively. Free radical capture experiments, FT-IR analysis and theoretical explorations further reveal that terminal alkynes and isocyanides can be catalytically transformed into an anionic intermediate through heterolysis pathways. This work provides secure and practical access to carbonylation as well as a new approach to aminocarbonylation of terminal alkynes.

Asymmetric Charge Distribution in Atomically Precise Metal Nanoclusters for Boosted CO2 Reduction Catalysis

Recently, atomically precise metal nanoclusters (NCs) have been widely applied in CO2 reduction reaction (CO2RR), achieving exciting activity and selectivity and revealing structure-performance correlation. However, at present, the efficiency of CO2RR is still unsatisfactory and cannot meet the requirements of practical applications. One of the main reasons is the difficulty in CO2 activation due to the chemical inertness of CO2. Constructing symmetry-breaking active sites is regarded as an effective strategy to promote CO2 activation by modulating electronic and geometric structure of CO2 molecule. In addition, in the subsequent CO2RR process, asymmetric charge distributed sites can break the charge balance in adjacent adsorbed C1 intermediates and suppress electrostatic repulsion between dipoles, benefiting for C-C coupling to generate C2+ products. Although compared to single atoms, metal nanoparticles, and inorganic materials the research on the construction of asymmetric catalytic sites in metal NCs is in a newly-developing stage, the precision, adjustability and diversity of metal NCs structure provide many possibilities to build asymmetric sites. This review summarizes several strategies of construction asymmetric charge distribution in metal NCs for boosting CO2RR, concludes the mechanism investigation paradigm of NCs-based catalysts, and proposes the challenges and opportunities of NCs catalysis.

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.

Supported Au single atoms and nanoparticles on MoS2 for highly selective CO2-to-CH3COOH photoreduction

Effectively controlling the selective conversion of CO2 photoreduction to C2 products presents a significant challenge. Here, we develop a heterojunction photocatalyst by controllably implanting Au nanoparticles and single atoms into unsaturated Mo atoms of edge-rich MoS2, denoted as Aun/Au1-CMS. Photoreduction of CO2 results in the production of CH3COOH with a selectivity of 86.4%, which represents a 6.4-fold increase compared to samples lacking single atoms, and the overall selectivity for C2 products is 95.1%. Furthermore, the yield of CH3COOH is 22.4 times higher compared to samples containing single atoms and without nanoparticles. Optical experiments demonstrate that the single atoms domains can effectively capture photoexcited electrons by the Au nanoparticles, or the local electric field generated by the nanoparticles promotes the transfer of photogenerated electrons in MoS2 to Au single atoms, prolonging the relaxation time of photogenerated electrons. Mechanistic investigations reveal that the orbital coupling of Au5d and Mo4d strengthens the oxygen affinity of Mo and carbon affinity of Au. The hybridized orbitals reduce energy splitting levels of CO molecular orbitals, aiding C-C coupling. Moreover, the Mo-Au dual-site stabilize the crucial oxygen-associated intermediate *CH2CO, thereby enhancing the selectivity towards CH3COOH. The cross-scale heterojunctions provide an effective strategy to simultaneously address the kinetical and thermodynamical limitations of CO2-to-CH3COOH conversion.

Boosting Solar-Driven CO2 Conversion to Ethanol via Single-Atom Catalyst with Defected Low-Coordination Cu-N2 Motif

Cu-based catalysts have been shown to selectively catalyze CO2 photoreduction to C2+ solar fuels. However, they still suffer from poor activity and low selectivity. Herein, we report a high-performance carbon nitride supported Cu single-atom catalyst featuring defected low-coordination Cu-N2 motif (Cu-N2-V). Lead many recently reported photocatalysts and its Cu-N3 and Cu-N4 counterparts, Cu-N2-V exhibits superior photocatalytic activity for CO2 reduction to ethanol and delivers 69.8 μmol g-1 h-1 ethanol production rate, 97.8 % electron-based ethanol selectivity, and a yield of ~10 times higher than Cu-N3 and Cu-N4. Revealed by the extensive experimental investigation combined with DFT calculations, the superior photoactivity of Cu-N2-V stems from its defected Cu-N2 configuration, in which the Cu sites are electron enriched and enhance electron delocalization. Importantly, Cu in Cu-N2-V exist in both Cu+ and Cu2+ valence states, although predominantly as Cu+. The Cu+ sites support the CO2 activation, while the co-existence of Cu+/Cu2+ sites are highly conducive for strong *CO adsorption and subsequent *CO-*CO dimerization enabling C-C coupling. Furthermore, the hollow microstructure of the catalyst also promotes light adsorption and charge separation efficiency. Collectively, these make Cu-N2-V an effective and high-performance catalyst for the solar-driven CO2 conversion to ethanol. This study also elucidates the C-C coupling reaction path via *CO-*CO to *COCOH and rate-determining step, and reveals the valence state change of partial Cu species from Cu+ to Cu2+ in Cu-N2-V during CO2 photoreduction reaction.

Photoelectrothermocatalytic reduction of CO2 to glycol via Cu2S/MoS2-Vs octahedral heterostructure with synergistic mechanism

The defects and interface engineering are efficient approaches to adjust the physical and chemical properties of nanomaterials to enhance catalytic performance. In this study, we report a new MOFs-driven porous Cu2S/MoS2-Vs octahedral semiconductor with heterostructure and photothermal effect. The introduction of sulfur vacancies directly improves the adsorption performance of CO2, and the formation of heterostructure significantly increases the charge transfer rate. The C-penetrating material obtained from MOFs not only acts as an octahedral skeleton support, but also gives photothermal effects under photoelectric conditions. The formation rate of sole C2 products in photoelectrocatalytic CO2 reduction by using Cu2S/MoS2-Vs heterostructure is up to 52 μM·h-1·cm-2 equal to the total electron transfer rate of 541 μM·h-1·cm-2. The carbene mechanism and reaction pathways were proposed and verified by 13CO2 isotopic labelling and operando Fourier transform infrared (FT-IR) spectra. The important intermediates of *CO2-, *CO, *CHO and *CHO-CHO were identified by operando FT-IR spectra. In the comparative experiments, the photothermal electrons are beneficial to C2 products. DFT calculations indicate that the presence of S vacancies (Vs) reduces the energy barrier for product generation.

Effective Reduction of CO2 with Aromatic Amines into N-Formamides Triggered by Noble-Free Metal-Organic Framework Catalysts Under Mild Conditions

The reductive transformation of carbon dioxide (CO2) into high-valued N‑formamides matches well with the atom economy and the sustainable development intention. Nevertheless, developing a noble-free metal catalyst under mild reaction conditions is desirable and challenging. Herein, a caged metal-organic framework (MOFs) [H2N(CH3)2]2{[Ni3(µ3-O)(XN)(BDC)3]·6DMF}n (1) (XN = 6″-(pyridin-4-yl)-4,2″:4″,4″'-terpyridine), H2BDC = terephthalic acid) is harvested, presenting high thermal and chemical stabilities. Catalytic investigation reveals that 1 as a renewable noble-free MOFs catalyst can catalyze the CO2 reduction conversion with aromatic amines tolerated by broad functional groups at least ten times, resulting in various formamides in excellent yields and selectivity under the mildest reaction system (room temperature and 1 bar CO2). Density functional theory (DFT) theoretical studies disclose the applicable reaction path, in which the CO2 hydrosilylation process is initiated by the [Ni3] cluster interaction with CO2 via η2-C, O coordination mode. This work may open up an avenue to seek high-efficiency noble-free catalysts in CO2 chemical reduction into high value-added chemicals.

CO2 Enrichment Boosts Highly Selective Infrared-Light-Driven CO2 Conversion to CH4 by UiO-66/Co9S8 Photocatalyst

Photocatalytic CO2 reduction to high-value chemicals is an attractive approach to mitigate climate change, but it remains a great challenge to produce a specific product selectively by IR light. Hence, UiO-66/Co9S8 composite is designed to couple the advantages of metallic photocatalysts and porous CO2 adsorbers for IR-light-driven CO2-to-CH4 conversion. The metallic nature of Co9S8 endows UiO-66/Co9S8 with exceptional IR light absorption, while UiO-66 dramatically enhances its local CO2 concentration, revealed by finite-element method simulations. As a result, Co9S8 or UiO-66 alone does not show observable IR-light photocatalytic activity, whereas UiO-66/Co9S8 exhibits exceptional activity. The CH4 evolution rate over UiO-66/Co9S8 reaches 25.7 µmol g-1 h-1 with ca.100% selectivity under IR light irradiation, outperforming most reported catalysts under similar reaction conditions. The X-ray absorption fine structure spectroscopy spectra verify the presence of two distinct Co sites and confirm the existence of metallic Co─Co bond in Co9S8. Energy diagrams analysis and transient absorption spectra manifest that CO2 reduction mainly occurs on Co9S8 for UiO-66/Co9S8, while density functional theory calculations demonstrate that high-electron-density Co1 sites are the key active sites, possessing lower energy barriers for further protonation of *CO, leading to the ultra-high selectivity toward CH4.

Flexible, recoverable, and efficient photocatalysts: MoS2/TiO2 heterojunctions grown on amorphous carbon-coated carbon textiles

Most traditional powder photocatalysts are not easily recovered. Herein, we report a flexible and recoverable photocatalyst with superior photocatalytic activity, in which MoS2/TiO2 heterojunctions are grown on amorphous carbon-coated carbon textiles (CT@C-MoS2/TiO2). Recoverable CT@C-MoS2/TiO2 textile was used to degrade 10 mg L-1 rhodamine B, leading to a degradation rate of up to 98.8 % within 30 min. Such a degradation rate is much higher than that of most of the reported studies. A density functional theory (DFT) calculation results illustrate charge transfer mechanism inside TiO2-C, MoS2-C, and MoS2/TiO2 heterojunctions, which shows that CT@C-MoS2/TiO2 textile with three electron separation channels has a high photogenerated carrier separation rate, which remarkably enhances the photocatalytic activity. Our work provides a novel strategy to design an efficient and recoverable photocatalyst with high activity.

Construction of Low-Cost Z-Scheme Heterojunction Cu2O/PCN-250 Photocatalysts Simultaneously for the Enhanced Photoreduction of CO2 to Alcohols and Photooxidation of Water

Solar-driven high-efficiency conversion of CO2 with water vapor into high-value-added alcohols is a promising approach for reducing CO2 emissions and achieving carbon neutrality. However, the rapid recombination of photogenerated carriers and low CO2 adsorption capacity of photocatalysts are usually the factors that limit their applicability. Herein, a series of low-cost Z-scheme heterostructures Cu2O/PCN-250-x are constructed by in situ growth of ultrasmall Cu2O nanoparticles on PCN-250. A systematic investigation revealed that there is a strong interaction between Cu2O nanoparticles and PCN-250. The resulting Cu2O/PCN-250-2 exhibits excellent photogenerated carrier separation efficiency and CO2 adsorption capacity, which dramatically promote the conversion of CO2 into alcohols. Notably, the total yield of 268 μmol gcat-1 for the production of CH3OH and CH3H2OH is superior to that of isolated PCN-250 and Cu2O. This study provides a new perspective for the design of a Cu2O nanoparticle/metal-organic framework Z-scheme heterojunction for the reduction of CO2 to alcohols with water vapor.

Recent advances in defect-engineered molybdenum sulfides for catalytic applications

Electrochemical energy conversion and storage driven by renewable energy sources is drawing ever-increasing interest owing to the needs of sustainable development. Progress in the related electrochemical reactions relies on highly active and cost-effective catalysts to accelerate the sluggish kinetics. A substantial number of catalysts have been exploited recently, thanks to the advances in materials science and engineering. In particular, molybdenum sulfide (MoSx) furnishes a classic platform for studying catalytic mechanisms, improving catalytic performance and developing novel catalytic reactions. Herein, the recent theoretical and experimental progress of defective MoSx for catalytic applications is reviewed. This article begins with a brief description of the structure and basic catalytic applications of MoS2. The employment of defective two-dimensional and non-two-dimensional MoSx catalysts in the hydrogen evolution reaction (HER) is then reviewed, with a focus on the combination of theoretical and experimental tools for the rational design of defects and understanding of the reaction mechanisms. Afterward, the applications of defective MoSx as catalysts for the N2 reduction reaction, the CO2 reduction reaction, metal-sulfur batteries, metal-oxygen/air batteries, and the industrial hydrodesulfurization reaction are discussed, with a special emphasis on the synergy of multiple defects in achieving performance breakthroughs. Finally, the perspectives on the challenges and opportunities of defective MoSx for catalysis are presented.

Fundamentals and Challenges of Engineering Charge Polarized Active Sites for CO2 Photoreduction toward C2 Products

ConspectusGlobal warming and climatic deterioration are partly caused by carbon dioxide (CO2) emission. Given this, CO2 reduction into valuable carbonaceous fuels is a win-win route to simultaneously alleviate the greenhouse effect and the energy crisis, where CO2 reduction into hydrocarbon fuels by solar energy may be a potential strategy. Up to now, most of the current photocatalysts photoconvert CO2 to C1 products. It is extremely difficult to achieve production of C2 products, which have higher economic value and energy density, due to the kinetic challenge of C-C coupling of the C1 intermediates. Therefore, to realize CO2 photoreduction to C2 fuels, design of high-activity photocatalysts to expedite the C-C coupling is significant. Besides, the current mechanism for CO2 photoreduction toward C2 fuels is usually uncertain, which is possibly attributed to the following two reasons: (1) It is arduous to determine the actual catalytic sites for the C-C coupling step. (2) It is hard to monitor the low-concentration active intermediates during the multielectron transfer step.Most traditional metal-based photocatalysts usually possess charge balanced active sites that have the same charge density. In this aspect, the neighboring C1 intermediates may also show the same charge distribution, which would lead to dipole-dipole repulsion, thus preventing C-C coupling for producing C2 fuels. By contrast, photocatalysts with charge polarized active sites possess obviously different charge distributions in the adjacent C1 intermediates, which can effectively suppress the electrostatic repulsion to steer the C-C coupling. Based on this analysis, higher asymmetric charge density on the active sites would be more beneficial to anchoring between the adjacent intermediates and active atoms in catalysts, which can boost C-C coupling.In this Account, we summarize various strategies, including vacancy engineering, doping engineering, loading engineering, and heterojunction engineering, for tailoring charge polarized active sites to boost the C-C coupling for the first time. Also, we overview diverse in situ characterization technologies, such as in situ X-ray photoelectron spectroscopy, in situ Raman spectroscopy, and in situ Fourier transform infrared spectroscopy, for determining charge polarized active sites and monitoring reaction intermediates, helping to reveal the internal catalytic mechanism of CO2 photoreduction toward C2 products. We hope this Account may help readers to understand the crucial function of charge polarized active sites during CO2 photoreduction toward C2 products and provide guidance for designing and preparing highly active catalysts for photocatalytic CO2 reduction.

Electronic Interactions on Platinum/(Metal-Oxide)-Based Photocatalysts Boost Selective Photoreduction of CO2 to CH4

By supporting platinum (Pt) and cadmium sulfide (CdS) nanoparticles on indium oxide (In2 O3 ), we fabricated a CdS/Pt/In2 O3 photocatalyst. Selective photoreduction of carbon dioxide (CO2 ) to methane (CH4 ) was achieved on CdS/Pt/In2 O3 with electronic Pt-In2 O3 interactions, with CH4 selectivity reaching to 100 %, which is higher than that on CdS/Pt/In2 O3 without electronic Pt-In2 O3 interactions (71.7 %). Moreover, the enhancement effect of electronic Pt-(metal-oxide) interactions on selective photoreduction of CO2 to CH4 also occurs by using other common metal oxides, such as photocatalyst supports, including titanium oxide, gallium oxide, zinc oxide, and tungsten oxide. The electronic Pt-(metal-oxide) interactions separate photogenerated electron-hole pairs and convert CO2 into CO2 δ- , which can be easily hydrogenated into CH4 via a CO2 δ- →HCOO*→HCO*→CH*→CH4 path, thus boosting selective photoreduction of CO2 to CH4 . This offers a new way to achieve selective photoreduction of CO2 .

Controlled Partial Linker Thermolysis in Metal-Organic Framework UiO-66-NH2 to Give a Single-Site Copper Photocatalyst for the Functionalization of Terminal Alkynes

Metal-organic frameworks (MOFs) with expanding porosity and tailored pore environments are intriguing for catalytic applications. We report herein a straightforward method of controlled partial linker thermolysis to introduce desirable mesopores into mono-ligand MOFs, which is different from the classical thermolyzing method that starts from mixed-linker MOFs. UiO-66-NH2 , after partial ligand thermolysis, exhibits significant mesoporosity, retained crystal structure, improved charge photogeneration and abundant anchoring sites, which is ideal to explore single-site photocatalysis. Atomically dispersed Cu is then accommodated in the tailored pore. The resulting single-site Cu catalyst exhibits excellent performance for photocatalytic alkylation and oxidation coupling for the functionalization of terminal alkynes. The study highlights the advantage of controlled partial linker thermolysis to synthesize hierarchical MOFs to achieve the advanced single-site photocatalysis.

CO2 Cycloaddition under Ambient Conditions over Cu-Fe Bimetallic Metal-Organic Frameworks

Carbon dioxide cycloaddition into fine chemicals is prospective technology to solve energy crisis and environmental issues. However, high temperature and pressure are usually required in the conventional cycloaddition reactions of CO2 with epoxides. Moreover, metal active sites play a vital role in the CO2 cycloaddition, but it is still unclear. Herein, we select the isostructural MOF-919-Cu-Fe and MOF-919-Cu-Al as models to promote the performance and clarify the effects of metal type on the CO2 cycloaddition. The MOF-919-Cu-Fe with exposed Fe and Cu Lewis acid sites reaches the CO2 cycloaddition with over 99.9% conversion and over 99.9% selectivity at room temperature and a 1 bar CO2 atmosphere, 3.0- and 52.6-fold higher than those of the MOF-919-Cu-Al with Al and Cu sites (33.8%) and the 1H-pyrazole-4-carboxylic acid, Fe, and Cu mixed system (1.9%), respectively. The proposed mechanism demonstrated that the exposed Fe3+ sites facilitate the ring opening of epoxide and CO2 activation to boost the CO2 cycloaddition reaction. This work provides a new insight to tune the catalytic sites of MOFs to achieve high performance for CO2 fixation.

One-pot solvothermal synthesis of In-doped amino-functionalized UiO-66 Zr-MOFs with enhanced ligand-to-metal charge transfer for efficient visible-light-driven CO2 reduction

Metal organic frameworks (MOFs) with high porosity and highly tunable physical/chemical properties can serve as heterogeneous catalysts for CO₂ photoreduction, but the application is hindered by the large band gap (E_g) and insufficient ligand-to-metal charge transfer (LMCT). In this study, a simple one-pot solvothermal strategy is proposed to prepare an amino-functionalized MOF (aU(Zr/In)) featuring an amino-functionalizing ligand linker and In-doped Zr-oxo clusters, which enables efficient CO₂ reduction driven with visible light. The amino functionalization leads to a significant reduction of E_g as well as a charge redistribution of the framework, allowing the absorption of visible light and the efficient separation of photogenerated carriers. Furthermore, the incorporation of In not only promotes the LMCT process by creating oxygen vacancies in Zr-oxo clusters, but also greatly lowers the energy barrier of the intermediates for CO₂-to-CO conversion. With the synergistic effects of the amino groups and the In dopants, the optimized aU(Zr/In) exhibits a CO production rate of 37.58 ± 1.06 μmol g^-1 h^-1, outperforming the isostructural University of Oslo-66- and Material of Institute Lavoisier-125-based photocatalysts. Our work demonstrates the potential of modifying MOFs with ligands and heteroatom dopants in metal-oxo clusters for solar energy conversion.

Janus Z-scheme heterostructure of ZnIn2S4/MoSe2/In2Se3 for efficient photocatalytic hydrogen evolution

Artificial manipulation of charge separation and transfer are central issues dominating hydrogen evolution reaction triggered via photocatalysis. Herein, through elaborate designing on the architecture, band alignment, and interface bonding mode, a sulfur vacancy-rich ZnIn₂S₄-based (Vs-ZIS) multivariate heterostructure ZnIn₂S₄/MoSe₂/In₂Se₃ (Vs-ZIS/MoSe₂/In₂Se₃) with specific Janus Z-scheme charge transfer mechanism is constructed through a two-step hydrothermal process. Steering by the Janus Z-scheme charge transfer mechanism, photogenerated electrons in the conduction band of MoSe₂ transfer synchronously to the valence band of Vs-ZIS and In₂Se₃, resulting in abundant highly-active photogenerated electrons reserved in the conduction band of Vs-ZIS and In₂Se₃, therefore significantly enhancing the photocatalytic activity of hydrogen evolution. Under visible light irradiation, the optimized Vs-ZIS/MoSe₂/In₂Se₃ with the mass ratio of MoSe₂ and In₂Se₃ to ZnIn₂S₄ at 3 % and 30 %, respectively, performs a high hydrogen evolution rate of 124.42 mmol·g^-1·h^-1, about 43.5-folds of the original ZIS photocatalyst. Besides, an apparent quantum efficiency (AQE) of 22.5 % at 420 nm and favorable durability are also achieved over Vs-ZIS/MoSe₂/In₂Se₃ photocatalyst. This work represents an important development in efficient photocatalysts and donates a sound foundation for the design of regulating charge transfer pathways.

Designing Heteroatom-Codoped Iron Metal-Organic Framework for Promotional Photoreduction of Carbon Dioxide to Ethylene

Rational engineering active sites and vantage defects of catalysts are promising but grand challenging task to enhance photoreduction CO₂ to high value-added C2 products. In this study, we designed an N,S-codoped Fe-based MIL-88B catalyst with well-defined bipyramidal hexagonal prism morphology via a facile and effective process, which was synthesized by addition of appropriate 1,2-benzisothiazolin-3-one (BIT) and acetic acid to the reaction solution. Under simulated solar irradiation, the designed catalyst exhibits high C₂ H₄ evolution yield of 17.7 μmol g^-1 ⋅h, which has been rarely achieved in photocatalytic CO₂ reduction process. The synergistic effect of Fe-N coordinated sites and reasonable defects in the N,S-codoped photocatalyst can accelerate the migration of photogenerated carriers, resulting in high electron density, and this in turn helps to facilitate the formation and dimerization of C-C coupling intermediates for C₂ H₄ effectively.

Efficient Strategy for U(VI) Photoreduction: Simultaneous Construction of U(VI) Confinement Sites and Water Oxidation Sites

Reduction of hexavalent uranium [U(VI)] by the photocatalytic method opens up a novel way to promote the selectivity, kinetics, and capacity during uranium removal, where organic molecules act as the sacrificial agents. However, the addition of sacrificial agents can cause a secondary environmental pollution and increase the cost. Here, a UiO-66-based photocatalyst (denoted as MnO_x/NH₂-UiO-66) simultaneously with efficient U(VI) confinement sites and water oxidation sites was successfully developed, achieving excellent U(VI) removal without sacrificial agents. In MnO_x/NH₂-UiO-66, the amino groups served as efficient U(VI) confinement sites and further decreased the U(VI) reduction potential. Besides, MnO_x nanoparticles separated the photogenerated electron-hole pairs and provided water oxidation sites. The U(VI) confinement sites and water oxidation sites jointly promoted the U(VI) photoreduction performance of MnO_x/NH₂-UiO-66, resulting in the removal ratio of MnO_x/NH₂-UiO-66 for U(VI) achieving 97.8% in 2 h without hole sacrifice agents. This work not only provides an effective UiO-66-based photocatalyst but also offers a strategy for effective U(VI) photoreduction.

Metabolic engineering using acetate as a promising building block for the production of bio-based chemicals

The production of biofuels and biochemicals derived from microbial fermentation has received a lot of attention and interest in light of concerns about the depletion of fossil fuel resources and climatic degeneration. However, the economic viability of feedstocks for biological conversion remains a barrier, urging researchers to develop renewable and sustainable low-cost carbon sources for future bioindustries. Owing to the numerous advantages, acetate has been regarded as a promising feedstock targeting the production of acetyl-CoA-derived chemicals. This review aims to highlight the potential of acetate as a building block in industrial biotechnology for the production of bio-based chemicals with metabolic engineering. Different alternative approaches and routes comprised of lignocellulosic biomass, waste streams, and C1 gas for acetate generation are briefly described and evaluated. Then, a thorough explanation of the metabolic pathway for biotechnological acetate conversion, cellular transport, and toxin tolerance is described. Particularly, current developments in metabolic engineering of the manufacture of biochemicals from acetate are summarized in detail, with various microbial cell factories and strategies proposed to improve acetate assimilation and enhance product formation. Challenges and future development for acetate generation and assimilation as well as chemicals production from acetate is eventually shown. This review provides an overview of the current status of acetate utilization and proves the great potential of acetate with metabolic engineering in industrial biotechnology.

Recent advancement in conjugated polymers based photocatalytic technology for air pollutants abatement: Cases of CO2, NOx, and VOCs

According to World Health Organization (WHO) survey, air pollution has become the major reason of several fatal diseases, which had led to the death of 7 million peoples around the globe. The 9 people out of 10 breathe air, which exceeds WHO recommendations. Several strategies are in practice to reduce the emission of pollutants into the air, and also strict industrial, scientific, and health recommendations to use sustainable green technologies to reduce the emission of contaminants into the air. Photocatalysis technology recently has been raised as a green technology to be in practice towards the removal of air pollutants. The scientific community has passed a long pathway to develop such technology from the material, and reactor points of view. Many classes of photoactive materials have been suggested to achieve such a target. In this context, the contribution of conjugated polymers (CPs), and their modification with some common inorganic semiconductors as novel photocatalysts, has never been addressed in literature till now for said application, and is critically evaluated in this review. As we know that CPs have unique characteristics compared to inorganic semiconductors, because of their conductivity, excellent light response, good sorption ability, better redox charge generation, and separation along with a delocalized π-electrons system. The advances in photocatalytic removal/reduction of three primary air-polluting compounds such as CO₂, NO_X, and VOCs using CPs based photocatalysts are discussed in detail. Furthermore, the synergetic effects, obtained in CPs after combining with inorganic semiconductors are also comprehensively summarized in this review. However, such a combined system, on to better charges generation and separation, may make the Adsorb & Shuttle process into action, wherein, CPs may play the sorbing area. And, we hope that, the critical discussion on the further enhancement of photoactivity and future recommendations will open the doors for up-to-date technology transfer in modern research.

Advances in Biomimetic Photoelectrocatalytic Reduction of Carbon Dioxide

Emerging photoelectrocatalysis (PEC) systems synergize the advantages of electrocatalysis (EC) and photocatalysis (PC) and are considered a green and efficient approach to CO2 conversion. However, improving the selectivity and conversion rate remains a major challenge. Strategies mimicking natural photosynthesis provide a prospective way to convert CO2 with high efficiency. Herein, several typical strategies are described for constructing biomimetic photoelectric functional interfaces; such interfaces include metal cocatalysts/semiconductors, small molecules/semiconductors, molecular catalysts/semiconductors, MOFs/semiconductors, and microorganisms/semiconductors. The biomimetic PEC interface must have enhanced CO2 adsorption capacity, preferentially activate CO2 , and have an efficient conversion ability; with these properties, it can activate CO bonds effectively and promote electron transfer and CC coupling to convert CO2 to single-carbon or multicarbon products. Interfacial electron transfer and proton coupling on the biomimetic PEC interface are also discussed to clarify the mechanism of CO2 reduction. Finally, the existing challenges and perspectives for biomimetic photoelectrocatalytic CO2 reduction are presented.

Photocatalytic CO2 conversion: from C1 products to multi-carbon oxygenates

Photocatalytic CO₂ conversion into high-value chemicals has been emerging as an attractive research direction in achieving carbon resource sustainability. The chemical products can be categorized into C1 and multi-carbon (C₂₊) products. In this review, we describe the recent research progress in photocatalytic CO₂ conversion systems from C1 products to multi-carbon oxygenates, and analyze the reasons related to their catalytic mechanisms, as the production of multi-carbon oxygenates is generally more difficult than that of C1 products. Then we discuss several examples in promoting the photoconversion of CO₂ to value-added multi-carbon products in the aspects of photocatalyst design, mass transfer control, determination of active sites, and intermediate regulation. Finally, we summarize perspectives on the challenges and propose potential directions in this fast-developing field, such as the prospect of CO₂ transformation to long-chain hydrocarbons like salicylic acid or even plastics.

Insight on Reaction Pathways of Photocatalytic CO2 Conversion

Photocatalytic CO₂ conversion to value-added chemicals is a promising solution to mitigate the current energy and environmental issues but is a challenging process. The main obstacles include the inertness of CO₂ molecule, the sluggish multi-electron process, the unfavorable thermodynamics, and the selectivity control to preferable products. Furthermore, the lack of fundamental understanding of the reaction pathways accounts for the very moderate performance in the field. Therefore, in this Perspective, we attempt to discuss the possible reaction mechanisms toward all C₁ and C₂ value-added products, taking into account the experimental evidence and theoretical calculation on the surface adsorption, proton and electron transfer, and products desorption. Finally, the remaining challenges in the field, including mechanistic understanding, reactor design, economic consideration, and potential solutions, are critically discussed by us.

Metallocavitins as Promising Industrial Catalysts: Recent Advances

The energy, material, and environmental problems of society require clean materials and impose an urgent need to develop effective chemical processes for obtaining and converting energy to ensure further sustainable development. To solve these challenges, it is necessary, first of all, to learn solar energy harvesting through the development of artificial photosynthesis. In our planet, water, carbon dioxide, and methane are such affordable and inexhaustible clean materials. Electro/photocatalytic water splitting, and also CO₂ and CH₄ transforming into valuable products, requires the search for relevant efficient and selective processes and catalysts. Of great interest is the emerging new generation of bioinspired catalysts—metallocavitins (MCs). MCs are attracting increasing attention of researchers as advanced models of metalloenzymes, whose efficiency and selectivity are well known. The primary field of MC application is fine organic synthesis and enantioselective catalysis. On the other hand, MCs demonstrate high activity for energy challenging reactions involving small gas molecules and high selectivity for converting them into valuable products. This mini-review will highlight some recent advances in the synthesis of organic substances using MCs, but its main focus will be on the rapid development of advanced catalysts for the activation of small molecules, such as H₂O, CO₂, and CH₄, and the prospects for creating related technological processes in the future.

Defected MoS2 Modified by Vanadium-Substituted Keggin-Type Polyoxometalates as Electrocatalysts for Triiodide Reduction in Dye-Sensitized Solar Cells

The rational design of efficient triiodide reduction reaction catalysts that are dependent on cheap and ample elements on Earth has become a challenge. As an extremely encouraging non-noble metallic catalyst, MoS₂ requires effective strategies to improve the site accessibility, inherent conductivity, and structural stability. Here, vanadium-substituted Keggin-type polyoxometalates (POMs) can be used as electron aggregates to modify manganese (Mn)-doped MoS₂ through the electrochemical deposition strategy, thereby improving the charge transfer ability of MoS₂ to I^-/I₃^- redox pairs and accelerating the reduction of I₃^-. Additionally, with the increase in the number of vanadium atoms substituted in POMs, the conduction band of POMs and MoS₂ can also match better, which effectively reduces the energy loss and is more conducive to charge transfer. Meanwhile, the deposition of POMs can improve the stability of metastable MoS₂. When POMs/MoS₂ materials are used as the counter electrodes of dye-sensitized solar cells, the power conversion efficiency (PCE) obtained is 7.27%, which is higher than that of platinum (Pt) (6.07%). The PCE can still maintain the initial 96% after 9 days. This work provides a valuable way for the improvement of platinum-free catalysts with minimal expense, basic process, high efficiency, and good stability.

Ni2P nanocrystals embedded Ni-MOF nanosheets supported on nickel foam as bifunctional electrocatalyst for urea electrolysis

It’s highly desired but challenging to synthesize self-supporting nanohybrid made of conductive nanoparticles with metal organic framework (MOF) materials for the application in the electrochemical field. In this work, we report the preparation of Ni₂P embedded Ni-MOF nanosheets supported on nickel foam through partial phosphidation (Ni₂P@Ni-MOF/NF). The self-supporting Ni₂P@Ni-MOF/NF was directly tested as electrode for urea electrolysis. When served as anode for urea oxidation reaction (UOR), it only demands 1.41 V (vs RHE) to deliver a current of 100 mA cm⁻². And the overpotential of Ni₂P@Ni-MOF/NF to reach 10 mA cm⁻² for hydrogen evolution reaction HER was only 66 mV, remarkably lower than Ni₂P/NF (133 mV). The exceptional electrochemical performance was attributed to the unique structure of Ni₂P@Ni-MOF and the well exposed surface of Ni₂P. Furthermore, the Ni₂P@Ni-MOF/NF demonstrated outstanding longevity for both HER and UOR. The electrolyzer constructed with Ni₂P@Ni-MOF/NF as bifunctional electrode can attain a current density of 100 mA cm⁻² at a cell voltage as low as 1.65 V. Our work provides new insights for prepare MOF based nanohydrid for electrochemical application.