Highly Efficient Electroreduction of CO2 to Ethanol via Asymmetric C-C Coupling by a Metal-Organic Framework with Heterodimetal Dual Sites

Single-Crystal Metal-Organic and Covalent Organic Framework Hybrids Enable Efficient Photoelectrochemical CO2 Reduction to Ethanol

Multicarbon alcohols produced through photochemical and electrochemical CO2 reduction reactions (CO2RR) are promising alternatives to fossil fuels; however, their selectivity and efficiency remain low due to the high energy barrier for C-C coupling and the competition from hydrocarbon production. Here, we present a strategy to enhance ethanol efficiency and selectivity via cooperative catalysis in porous structures for photoelectrochemical (PEC) CO2RR. Using a coordination-templated strategy, we synthesized single crystals of MOF-COF (MOCOF) hybrids with metalloporphyrins, with their structures determined by single-crystal 3D electron diffraction. The porous frameworks featuring adjacent confined metalloporphyrins efficiently capture and cooperatively activate CO2, achieving outstanding PEC CO2-to-ethanol conversion. Particularly, the Pt-MOCOF delivers a Faradaic efficiency (FE) of 83.5% at -1.0 V with 91.7% carbon selectivity, surpassing state-of-the-art COF or MOF catalysts and ranking it among the top-performing catalysts. The catalyst system displays remarkable stability, maintaining 95% of its activity after 100 h of continuous operation. Experiments and theoretical calculations revealed that the cooperative catalyst enriches and stabilizes intermediates in the channels, guiding the reaction pathway toward ethanol production.

Recent Advances in MOF-Based Dual-Atom Catalysts for CO2 Reduction

In recent years, the development of efficient catalysts for photo-/electro-catalytic CO2 reduction reaction (CO2RR) has become a major research focus due to growing environmental concerns and energy demands. Dual-atom catalysts (DACs), composed of two metal atoms with suitable metal-metal distance integrated into the supports, have shown great promise in enhancing catalytic performance via the dual-metal synergistic catalysis (DMSC) effect. This review highlights the advancements in Metal-organic framework (MOF)-based DACs, which combine the high atomic efficiency of DACs with tunable and defined structures and high metal loadings. In this review, we summarized the recent developments on the synthesis strategies of MOF-based DACs and their applications in CO2RR, focusing on the role of DMSC effect in improving catalytic activity, stability, and selectivity. Additionally, we also discuss the influence of the local electronic structure, coordination environment, and metal atom interactions on catalytic performance. This review aims to provide a comprehensive understanding of MOF-based DACs and offers insights into their future potential in sustainable energy conversion.

Hydroxylation of Cu Sites Enhances Selectivity of Electrosynthesis of Ethanol via Tandem Reduction of CO2

Electrochemical conversion of CO2 into value-added multi-carbon products is highly attractive for CO2 utilization using sustainable electricity energy. However, achieving high ethanol selectivity of copper-based catalysts remains challenging due to the competing side reactions such as ethylene formation. Herein, a novel electrocatalyst, PANI-Ag/Cu-OH is reported, comprising of polyaniline-supported silver single atoms coupled with hydroxyl-modified copper clusters. Tandem reduction of CO2 into ethanol with a high selectivity is realized by coupling CO formation on Ag site and further reduction on hydroxylated Cu sites. The synergistic approach enables a high Faradaic efficiency of 68.9% for ethanol with a current density of -263.8 mA cm-2 at -0.78 V versus RHE in alkaline media. CO-TPD and in situ infrared spectra studies reveal that strong CO adsorption and Cu+ species stabilized by hydroxyl groups are crucial for asymmetric C-C coupling and stabilization of the ethanol intermediates, leading to the enhanced ethanol selectivity.

Theoretical understanding of CO2 reduction products on nitrogen-doped graphene supported dual-atom catalysts

In recent years, nitrogen-doped graphene supported dual-atom catalysts (DAC@NC) for the CO2 reduction reaction (CO2RR) have attracted widespread research interest. Although some DAC structures for deep reduction C1 products and C2 products have been proposed in previous theoretical calculations, the desired products are still difficult to be realized in experiments. This work systematically investigates the reaction pathways and products of CO2 reduction on bimetallic DAC@NC (M1-M2@NC, M1, M2 = Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, and Pt) by first-principles calculations. After excluding improper M1-M2@NC due to catalyst poisoning and hydrogen evolution competition, C-C coupling processes always have much higher free-energy increments than the corresponding hydrogenation, making it difficult to form multi-carbon structures. For most of the C1 intermediates on M1-M2@NC, the free-energy increments of C-C coupling are higher than 0.8 eV. Some C1 intermediates could couple with a second carbon, but this process is much more difficult than hydrogenation toward C1 products. This work reveals why C2 products are still difficult to be achieved for the CO2RR on M1-M2@NC and identifies the M1-M2 combinations for deep reduction C1 products (methane and methanol), which is inspiring for the future design of CO2RR catalysts.

Tuning Multi-Active Sites in Cu Catalyst via Ag/Ni Doping for Enhanced CO2 Electroreduction to C2+ Products

Electrochemical CO2 reduction (ECR) to C2+ products is a promising sustainable carbon conversion pathway, yet simultaneously achieving high Faradaic efficiency (FE) and current density remains a challenge. Herein, we found that creating Cu-Ag-Ni multi-metal sites could effectively modulate the adsorption energies of *H and *CO on the catalyst surface, thereby achieving highly efficient ECR to synthesize C2+ products. In situ measurements coupling theoretical calculations indicated that by systematically altering the spatial arrangement and distribution of active sites in Cu-Ag-Ni catalysts, the electronic structure and the local *CO coverage on the Cu surface could be tuned, consequently steering the ECR to C2+ pathway. In particular, Cu-Ag-Ni catalyst with dispersed multi-sites (CuxAgNi DNPs) could more effectively reduce the energy barrier for C─C coupling than Cu-Ag-Ni catalyst with phase-separated multi-sites (CuxAgNi PNPs). As a result, the Cu40AgNi DNPs catalyst with dispersed multi-sites yielded C2+ products with a FE of 93.2% and a current density up to 818.1 mA cm-2 at -1.38 V versus reversible hydrogen electrode (vs. RHE), which are higher than most reported up to date for C2+ production. This work provides a methodology for designing robust multi-metallic ECR catalysts with tailored multi-active site configurations.

Accurate Thermal Resection of Atomically Precise Copper Clusters to Achieve Near-IR Light-Driven CO2 Reduction

Atomically precise copper clusters are desirable as catalysts for elaborating the structure-activity relationships. The challenge, however, lies in their tendency to sinter when protective ligands are removed, resulting in the destruction of the structural integrity of the model system. Herein, a copper-sulfur-nitrogen cluster [Cu8(StBu)4(PymS)4] (denoted as Cu8SN) is synthesized by using a mixed ligand approach with strong chelating 2-mercaptopyrimidine (PymSH) ligands and relatively weak monodentate tert-butyl mercaptan ligands. A precise thermal-resection strategy is applied to selectively peel only the targeted weak ligands off, which induces a structural transformation of the initial Cu8 cluster into a new and more stable Cu-S-N cluster [Cu8(S)2(PymS)4] (denoted as Cu8SN-T). The residual bridging S2- within the metal core forms asymmetric Cu-S species with a near-infrared (NIR) response, which endows Cu8SN-T with the capability for full-spectrum responsive CO2 photoreduction, achieving a ≈100% CO2-to-CO selectivity. Especially for NIR-driven CO2 reduction, it has a CO evolution of 42.5 µmol g-1 under λ > 780 nm. Importantly, this work represents the first NIR light-responsive copper cluster for efficient CO2 photoreduction and opens an avenue for the precise manipulation of metal cluster structures via a novel thermolysis strategy to develop unprecedented functionalized metal cluster materials.

Asymmetric Co-Ru Heterostructure Catalyst for Surface-Plasmon-Enhanced Photothermocatalytic CO Hydrogenation to Fuels

Photothermal Fischer-Tropsch synthesis (FTS) aims to convert carbon monoxide (CO) into value-added long-chain hydrocarbons (C5+) under milder conditions, but the efficient C-C coupling of C1 intermediates remains challenging. Herein, a carbon-supported plasmonic CoRu5@C catalyst has been successfully constructed for promoting C-C coupling. Experimental results demonstrate that under ambient pressure and photothermal conditions at 250 °C, CoRu5@C exhibits a C5+ selectivity of 98.9% and FTS activity of 321.4 mmol gcat-1 h-1. Structural characterizations and finite element method simulations indicate that Ru-induced lattice strain in the Co-Ru heterogeneous catalyst boosts energetic charge carrier migration, promoting CO adsorption and activation. A series of in situ experiments reveal that electron-rich Co sites in the Co-Ru heterogeneous catalyst diminish C1 intermediate repulsion, boosting C-C coupling efficiency in the FTS process. This research not only provides an innovative approach to overcoming the challenges in CO hydrogenation selectivity and the synthesis of high-value fuels but also offers significant contributions to the development of sustainable energy technologies.

Progress in Cu-Based Catalyst Design for Sustained Electrocatalytic CO2 to C2+ Conversion

The electrocatalytic conversion of CO2 into valuable multi-carbon (C2+) products using Cu-based catalysts has attracted significant attention. This review provides a comprehensive overview of recent advances in Cu-based catalyst design to improve C2+ selectivity and operational stability. It begins with an analysis of the fundamental reaction pathways for C2+ formation, encompassing both established and emerging mechanisms, which offer critical insights for catalyst design. In situ techniques, essential for validating these pathways by real-time observation of intermediates and material evolution, are also introduced. A key focus of this review is placed on how to enhance C2+ selectivity through intermediates manipulation, particularly emphasizing catalytic site construction to promote C─C coupling via increasing *CO coverage and optimizing protonation. Additionally, the challenge of maintaining catalytic activity under reaction conditions is discussed, highlighting the reduction of active charged Cu species and materials reconstruction as major obstacles. To address these, the review describes recent strategies to preserve active sites and control materials evolution, including novel catalyst design and the utilization and mitigation of reconstruction. By presenting these developments and the challenges ahead, this review aims to guide future materials design for CO2 conversion.

Bimetallic effects in carbon dioxide electroreduction

As a clean and sustainable technology, electrocatalytic carbon dioxide reduction reaction (ECO2RR) occupies a central position in the global energy transformation and climate change strategy. Compared with single metallic catalysts, bimetallic catalysts have many advantages, such as the synergistic effect between bimetals, enhanced CO2 adsorption capacity, and lower reaction energy barriers, which make them widely used in the CO2RR for the generation of multi-carbon products. This review systematically summarizes the latest advances in bimetallic effects for the CO2RR. In this paper, we start with a classified introduction on the CO2RR mechanisms, followed by a comprehensive discussion of the structure-activity relationships of various bimetallic catalysts, including regulation of metal centers, regulation of the distance between metal sites, regulation of the coordination environment, interface engineering, and strain engineering. Next, we showcase the advantages of bimetallic catalysts in the CO2RR. Then, the research progress of typical bimetallic catalysts for the ECO2RR is discussed, including diatomic catalysts, bimetallic alloys, bimetallic MOFs and bimetallic COFs. Finally, we summarize the challenges faced today from the five aspects of product selectivity, catalyst stability, product purification, theoretical simulations and in situ characterization techniques and put forward the research direction to promote the industrialization process of CO2RR.

Two-dimensional conjugated metal-organic frameworks for electrochemical energy conversion and storage

Effective electrocatalysts and electrodes are the core components of energy conversion and storage systems for sustainable carbon and nitrogen cycles to achieve a carbon-neutral economy. Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have emerged as multifunctional materials for electrochemical applications benefiting from their similarity to graphene with remarkable conductivity, abundant active sites, devisable components, and well-defined crystalline structures. In this review, the structural design strategies to establish active components with a maximum degree through redox-active ligand assembly in 2D c-MOFs are briefly summarized. Next, recent representative examples of 2D c-MOFs applied in electrocatalysis (hydrogen/oxygen evolution and oxygen/carbon dioxide/nitrogen reduction) and energy storage systems (supercapacitors and batteries) are introduced. The synergistic effect of multiple components in 2D c-MOFs is particularly emphasized for enhanced performance in electrochemical energy conversion and storage systems. Finally, an outlook and challenges are proposed for realizing more active components, elucidating the reaction mechanism involving the derived structures, and achieving low-cost economy in practical applications.

Electrocatalytic Reduction of CO2 to Long-Chain Hydrocarbons: Investigating the Asymmetric C-C Coupling Mechanism on Pd3Au Catalysts

The electrochemical reduction of CO2 to high-energy-density hydrocarbons is pivotal for addressing energy and environmental challenges. Understanding the mechanisms underlying the conversion of CO2 to long-chain hydrocarbons is both crucial and complex. In this study, we employed density functional theory (DFT) calculations to investigate the C-C coupling mechanisms responsible for the formation of C2-C4 products on Pd3Au catalysts. Our findings highlight the sequential formation of C2-C1 bonds via asymmetric C-C coupling as a critical pathway for generating C3 product, which is essential for controlling product selectivity. Detailed analysis of coupling reactions involving CCH2* and CCH3* intermediates with various C1 species indicates that these asymmetric coupling events are energetically favorable and play a decisive role in the selective assembly of carbon atoms into longer hydrocarbon chains. Moreover, we propose a mechanism wherein the asymmetric coupling of C1-C3 intermediate leads to a diverse array of C4 products. This process underscores the importance of CH2 group coupling with C3 intermediates in forming long-chain hydrocarbons. Our work provides valuable insights into optimizing catalyst design for improved selectivity towards higher hydrocarbons in CO2 reduction processes.

Elaborate Designed Three-Dimensional Hierarchical Conductive MOF/LDH/CF Nanoarchitectures for Superior Capacitive Deionization

Rational exploration of cost-effective, durable, and high-performance electrode materials is imperative for advancing the progress of capacitive deionization (CDI). The integration of multicomponent layered double hydroxides (LDHs) with conjugated conductive metal-organic frameworks (c-MOFs) to fabricate bifunctional heterostructure electrode materials is considered a complex but promising strategy. Herein, the fabrication of elaborately designed three-dimensional hierarchical conductive MOF/LDH/CF nanoarchitectures (M-CAT/LDH/CF) as CDI anodes via a controllable grafted-growth strategy is reported. In this assembly, carbon fiber (CF) provides exceptional electrical conductivity facilitating rapid ion transfer and acts as a sturdy foundation for even distribution of NiCoCu-LDH nanosheets. Moreover, the well-ordered NiCoCu-LDH further acts as interior templates to create an interface by embedding c-MOFs and aligning two crystal lattice systems, facilitating the graft growth of c-MOFs/LDH heterostructures along the LDH nanosheet arrays on CF, leading to accelerated ion diffusion kinetics. Density functional theory (DFT) confirms the unique structure of M-CAT/LDH/CF promotes interfacial charge transfer from NiCoCu-LDH to M-CAT. This enhancement accelerates ion transfer, decreases ion migration energy, and leads to better ion diffusion kinetics and a smoother Cl- shuttle. Accordingly, the asymmetrical M-CAT/LDH/CF cell exhibited superior specific capacitance (315 F g-1), excellent salt adsorption capacity (147.8 mg g-1), rapid rate (21.1 mg g-1 min-1), and impressive cyclic stability (91.4 % retention rate). This work offers valuable insights for designing heterostructure electrode materials based on three-dimensional interconnected networks, contributing to further advancements in CDI technology.

Cu-Sb Atomic Pair Site in Metal Halide Perovskite for CO2 Reduction to Methanol

Electrochemical conversion of CO2 into methanol has received extensive attention in recent years since methanol is an efficient energy carrier and industrial feedstock. However, the selectivity to methanol remains unsatisfied. In this work, Sb-doped Cs3Cu2I5 is first and rationally developed for CO2 electrochemical reduction, achieving remarkable high selectivity of methanol. UV-vis absorption, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations show that the Sb dopants narrow the band gap of Cs3Cu2I5 and enhance the metal-ligand hybridization due to the introduction of Sb 5p orbitals, which accordingly enhance the charge transfer. In addition, the Cu-Sb pair in Sb@Cs3Cu2I5 perovskite synergistically catalyzes the CO2 conversion. The Cu sites serve for CO2 absorption and activation, while the Sb sites stabilize the intermediate *OCH2 through the Sb-O bond due to superior oxygen affinity. The plasma-treated sample with electron-deficient Sb exhibits the best methanol selectivity as high as 88.38%. This work provides new insight into highly efficient metal halide perovskite-based catalysts for CO2 electrochemical conversion.

Regulating Interfacial Hydrogen-Bonding Networks by Implanting Cu Sites with Perfluorooctane to Accelerate CO2 Electroreduction to Ethanol

Efficient CO2 electroreduction (CO2RR) to ethanol holds promise to generate value-added chemicals and harness renewable energy simultaneously. Yet, it remains an ongoing challenge due to the competition with thermodynamically more preferred ethylene production. Herein, we presented a CO2 reduction predilection switch from ethylene to ethanol (ethanol-to-ethylene ratio of ~5.4) by inherently implanting Cu sites with perfluorooctane to create interfacial noncovalent interactions. The 1.83 %F-Cu2O organic-inorganic hybrids (OIHs) exhibited an extraordinary ethanol faradaic efficiency (FEethanol) of ∼55.2 %, with an impressive ethanol partial current density of 166 mA cm-2 and excellent robustness over 60 hours of continuous operation. This exceptional performance ranks our 1.83 %F-Cu2O OIHs among the best-performing ethanol-oriented CO2RR electrocatalysts. Our findings identified that C8F18 could strengthen the interfacial hydrogen bonding connectivity, which consequently promotes the generation of active hydrogen species and preferentially favors the hydrogenation of *CHCOH to *CHCHOH, thus switching the reaction from ethylene-preferred to ethanol-oriented. The presented investigations highlight opportunities for using noncovalent interactions to tune the selectivity of CO2 electroreduction to ethanol, bringing it closer to practical implementation requirements.

Two-Dimensional Conjugated Metal-Organic Frameworks for Photochemical Transformations

Photochemical transformation represents an attractive pathway for the conversion of earth-abundant resources, such as H2O, CO2, O2, and N2, into valuable chemicals by utilizing sunlight as an energy source. Recently, two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have emerged as the focal points in the field of photo-to-chemical conversion due to their advantages in light harvesting, electrical conductivity, mass transport, tunable electronic and porous structures, as well as abundant active sites. In this review, we highlight various physical and chemical features of 2D c-MOFs that can contribute to enhanced photo-induced exciton generation, charge transport, proton migration and redox catalysis. Then, the existing strategies to integrate suitable light absorbers and/or co-catalysts onto 2D c-MOFs for photochemical transformations (with a particular focus on H2 evolution, CO2 reduction and O2 reduction) have been discussed. Finally, the challenges and opportunities of using 2D c-MOFs in other photochemical applications (e.g., N2 fixation, organic synthesis, and environmental remediation) are assessed.

Promotion of C─C Coupling in the CO2 Electrochemical Reduction to Valuable C2+ Products: From Micro-Foundation to Macro-Application

The electrochemical CO2 reduction reaction (CO2RR) to valuable C2+ products emerges as a promising strategy for converting intermittent renewable energy into high-energy-density fuels and feedstock. Leveraging its substantial commercial potential and compatibility with existing energy infrastructure, the electrochemical conversion of CO2 into multicarbon hydrocarbons and oxygenates (C2+) holds great industrial promise. However, the process is hampered by complex multielectron-proton transfer reactions and difficulties in reactant activation, posing significant thermodynamic and kinetic barriers to the commercialization of C2+ production. Addressing these barriers necessitates a comprehensive approach encompassing multiple facets, including the effective control of C─C coupling in industrial electrolyzers using efficient catalysts in optimized local environments. This review delves into the advancements and outstanding challenges spanning from the microcosmic to macroscopic scales, including the design of nanocatalysts, optimization of the microenvironment, and the development of macroscopic electrolyzers. By elucidating the influence of the local electrolyte environment, and exploring the design of potential industrial flow cells, guidelines are provided for future research aimed at promoting C─C coupling, thereby bridging microscopic insights and macroscopic applications in the field of CO2 electroreduction.

Br, O-Modified Cu(111) Interface Promotes CO2 Reduction to Multicarbon Products

Electrochemical reduction of CO2 to multicarbon (C2+) products with added value represents a promising strategy for achieving a carbon-neutral economy. Precise manipulation of the catalytic interface is imperative to control the catalytic selectivity, particularly toward C2+ products. In this study, a unique Cu/UIO-Br interface is designed, wherein the Cu(111) plane is co-modified simultaneously by Br and O from UIO-66-Br support. Such Cu/UIO-Br catalytic interface demonstrates a superior Faradaic efficiency of ≈53% for C2+ products (ethanol/ethylene) and the C2+ partial current density reached 24.3 mA cm-2 in an H-cell electrolyzer. The kinetic isotopic effect test, in situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory calculations have been conducted to elucidate the catalytic mechanism. The Br, O co-modification on the Cu(111) interface enhanced the adsorption of CO2 species. The hydrogen-bond effect from the doped Br atom regulated the kinetic processes of *H species in CO2RR and promoted the formation of *COH intermediate. The formed *COH facilitates the *CO-*COH coupling and promotes the C2+ selectivity finally. This comprehensive investigation not only provides an in-depth study and understanding of the catalytic process but also offers a promising strategy for designing efficient Cu-based catalysts with exceptional C2+ products.

Intermolecular Forces-Oriented Growth of MOF-on-MOF Heterostructures

Well-controlled conjugation of distinct metal-organic frameworks (MOFs) with dissimilar components and structures into a multi-component MOF system is important for the design of myriad materials with structural complexity, integrated properties, and desired applications. Herein, we developed an interesting integration strategy that relies on intermolecular force, and which can overcome the difference in lattice parameters. The strategy uses the pre-formed MOF matrixes as seeds to direct the self-assembly of secondary MOF particles for the construction of hybrid MOFs. As a proof of concept, the representative core-satellite-type Ni-MOF@ZIF-8 and core-shell-type MOF-74@ZIF-8 heterostructures were achieved. Theory calculations elucidate the uncommon formation of well-defined hybrid MOFs by self-assembly of secondary ZIF-8 particles to anchor on Ni-MOF or MOF-74 seed surface via hydrogen bonds and van der Waals interactions. We anticipate that this work opens an avenue to design the multi-component MOF systems from different MOFs with lattice mismatching.

Mesostructure-Specific Configuration of *CO Adsorption for Selective CO2 Electroreduction to C2+ Products

The multi-carbon (C2+) alcohols produced by electrochemical CO2 reduction, such as ethanol and n-propanol, are considered as indispensable liquid energy carriers. In most C-C coupling cases, however, the concomitant gaseous C2H4 product results in the low selectivity of C2+ alcohols. Here, we report rational construction of mesostructured CuO electrocatalysts, specifically mesoporous CuO (m-CuO) and cylindrical CuO (c-CuO), enables selective distribution of C2+ products. The m-CuO and c-CuO show similar selectivity towards total C2+ products (≥76 %), but the corresponding predominant products are C2+ alcohols (55 %) and C2H4 (52 %), respectively. The ordered mesostructure not only induces the surface hydrophobicity, but selectively tailors the adsorption configuration of *CO intermediate: m-CuO prefers bridged adsorption, whereas c-CuO favors top adsorption as revealed by in situ spectroscopies. Computational calculations unravel that bridged *CO adsorbate is prone to deep protonation into *OCH3 intermediate, thus accelerating the coupling of *CO and *OCH3 intermediates to generate C2+ alcohols; by contrast, top *CO adsorbate is apt to undergo conventional C-C coupling process to produce C2H4. This work illustrates selective C2+ products distribution via mesostructure manipulation, and paves a new path into the design of efficient electrocatalysts with tunable adsorption configuration of key intermediates for targeted products.

Fabrication of Ultrahigh-Loading Dual Copper Sites in Nitrogen-Doped Porous Carbons Boosting Electroreduction of CO2 to C2H4 Under Neutral Conditions

Synthesis of high-loading atomic-level dispersed catalysts for highly efficient electrochemical CO2 reduction reaction (eCO2RR) to ethylene (C2H4) in neutral electrolyte remain challenging tasks. To address common aggregation issues, a host-guest strategy is employed, by using a metal-azolate framework (MAF-4) with nanocages as the host and a dinuclear Cu(I) complex as the guest, to form precursors for pyrolysis into a series of nitrogen-doped porous carbons (NPCs) with varying loadings of dual copper sites, namely NPCMAF-4-Cu2-21 (21.2 wt%), NPCMAF-4-Cu2-11 (10.6 wt%), and NPCMAF-4-Cu2-7 (6.9 wt%). Interestingly, as the loading of dual copper sites increased from 6.9 to 21.2 wt%, the partial current density for eCO2RR to yield C2H4 also gradually increased from 38.7 to 93.6 mA cm-2. In a 0.1 m KHCO3 electrolyte, at -1.4 V versus reversible hydrogen electrode (vs. RHE), NPCMAF-4-Cu2-21 exhibits the excellent performance with a Faradaic efficiency of 52% and a current density of 180 mA cm-2. Such performance can be attributed to the presence of ultrahigh-loading dual copper sites, which promotes C─C coupling and the formation of C2 products. The findings demonstrate the confinement effect of MAF-4 with nanocages is conducive to the preparation of high-loading atomic-level catalysts.

Isomeric Cu(I) Azolate Frameworks Showing Contrasting Electrocatalytic CO2 Reduction Selectivities and Stabilities

Metal‒organic frameworks have attracted wide interest in the electrocatalytic CO2 reduction reaction (eCO2RR), but their differences of performances originated from chemical composition and stabilities are rarely concerned. Here, isomeric Cu(I) triazolate frameworks (MAF-2Fa and MAF-2Fb) with similar thermal/chemical stabilities but very different coordination modes are used for eCO2RR studies. MAF-2Fa with monotypic planar dinuclear Cu(I) coordination mode achieves high selectivity for C2H4 (53%) and C2 products (70%), with almost unchanged over a wide potential window (‒1.1 to ‒1.5 V), making it among one of the best Cu-complex electrocatalysts. In contrast, MAF-2Fb with multiple Cu(I) coordination modes (including planar/bent dinuclear, linear mononuclear, and trigonal mononuclear ones) showed low C2/C1 products without significant differences. More interestingly, MAF-2Fa can maintain its performance for at least 8 h, whereas MAF-2Fb decomposed into inorganics with inferior performance after 1.5 h. The significant differences of eCO2RR selectivities and stabilities are elucidated by computational simulations and operando electrochemical tests.

Radiation-Synthesized Metal-Organic Frameworks with Ligand-Induced Lewis Pairs for Selective CO2 Electroreduction

The electrochemical activation of inert CO2 molecules through C─C coupling reactions under ambient conditions remains a significant challenge but holds great promise for sustainable development and the reduction of CO2 emission. Lewis pairs can capture and react with CO2, offering a novel strategy for the electrosynthesis of high-value-added C2 products. Herein, an electron-beam irradiation strategy is presented for rapidly synthesizing a metal-organic framework (MOF) with well-defined Lewis pairs (i.e., Cu- Npyridinic). The synthesized MOFs exhibit a total C2 product faradic efficiency of 70.0% at -0.88 V versus RHE. In situ attenuated total reflection Fourier transform infrared and Raman spectra reveal that the electron-deficient Lewis acidic Cu sites and electron-rich Lewis basic pyridinic N sites in the ligand facilitate the targeted chemisorption, activation, and conversion of CO2 molecules. DFT calculations further elucidate the electronic interactions of key intermediates in the CO2 reduction reaction. The work not only advances Lewis pair-site MOFs as a new platform for CO2 electrochemical conversion, but also provides pioneering insights into the underlying mechanisms of electron-beam irradiated synthesis of advanced nanomaterials.

Experimental and Theoretical Insights into Single Atoms, Dual Atoms, and Sub-Nanocluster Catalysts for Electrochemical CO2 Reduction (CO2RR) to High-Value Products

Electrocatalytic carbon dioxide (CO2) conversion into valuable chemicals paves the way for the realization of carbon recycling. Downsizing catalysts to single-atom catalysts (SACs), dual-atom catalysts (DACs), and sub-nanocluster catalysts (SNCCs) has generated highly active and selective CO2 transformation into highly reduced products. This is due to the introduction of numerous active sites, highly unsaturated coordination environments, efficient atom utilization, and confinement effect compared to their nanoparticle counterparts. Herein, recent Cu-based SACs are first reviewed and the newly emerged DACs and SNCCs expanding the catalysis of SACs to electrocatalytic CO2 reduction (CO2RR) to high-value products are discussed. Tandem Cu-based SAC-nanocatalysts (NCs) (SAC-NCs) are also discussed for the CO2RR to high-value products. Then, the non-Cu-based SACs, DACs, SAC-NCs, and SNCCs and theoretical calculations of various transition-metal catalysts for CO2RR to high-value products are summarized. Compared to previous achievements of less-reduced products, this review focuses on the double objective of achieving full CO2 reduction and increasing the selectivity and formation rate toward C-C coupled products with additional emphasis on the stability of the catalysts. Finally, through combined theoretical and experimental research, future outlooks are offered to further develop the CO2RR into high-value products over isolated atoms and sub-nanometal clusters.

Confinement Synthesis of Atomic Copper-Anchored Polymeric Carbon Nitride in Crystalline UiO-66-NH2 for High-Performance CO2-to-CH3OH Photocatalysis

Photocatalytic CO2 reduction to value-added fuels displays an attractive scenario to enhance energy supply and reduce global warming. We report herein the confinement synthesis of polymeric carbon nitride (PCN) incorporating with Cu single atoms (CuSAs) inside the crystalline UiO-66-NH2, which combines the merits of heterojunction photocatalysis and single-atom catalysis (SAC) to achieve high-performance CO2-to-CH3OH conversion. A series of spectral studies displays the formation of CuSAs@PCN inside the crystalline UiO-66-NH2. Remarkably, the ternary composite shows an excellent photocatalytic turnover frequency of 4.15 mmol ⋅ h-1 ⋅ g-1 for CO2-to-CH3OH conversion. Theoretical and experimental studies demonstrate the doping of CuSAs, as well as the formation of type-II heterojunction, are causal factors to achieve CH3OH generation. The study provides new insights designing high-performance photocatalyst for CO2 conversion to fuels at atomic scale.

Electrolyte Composition-Dependent Product Selectivity in CO2 Reduction with a Porphyrinic Metal-Organic Framework Catalyst

A copper porphyrin-derived metal-organic framework electrocatalyst, FICN-8, was synthesized and its catalytic activity for CO2 reduction reaction (CO2RR) was investigated. FICN-8 selectively catalyzed electrochemical reduction of CO2 to CO in anhydrous acetonitrile electrolyte. However, formic acid became the dominant CO2RR product with the addition of a proton source to the system. Mechanistic studies revealed the change of major reduction pathway upon proton source addition, while catalyst-bound hydride (*H) species was proposed as the key intermediate for formic acid production. This work highlights the importance of electrolyte composition on CO2RR product selectivity.

Asymmetrically Coordinated Cu Dual-Atom-Sites Enables Selective CO2 Electroreduction to Ethanol

Electrochemical reduction of CO2 (CO2RR) to value-added liquid fuels is a highly attractive solution for carbon-neutral recycling, especially for C2+ products. However, the selectivity control to preferable products is a great challenge due to the complex multi-electron proton transfer process. In this work, a series of Cu atomic dispersed catalysts are synthesized by regulating the coordination structures to optimize the CO2RR selectivity. Cu2-SNC catalyst with a uniquely asymmetrical coordinated CuN2-CuNS site shows high ethanol selective with the FE of 62.6% at -0.8 V versus RHE and 60.2% at 0.9 V versus RHE in H-Cell and Flow-Cell test, respectively. Besides, the nest-like structure of Cu2-SNC is beneficial to the mass transfer process and the selection of catalytic products. In situ experiments and theory calculations reveal the reaction mechanisms of such high selectivity of ethanol. The S atoms weaken the bonding ability of the adjacent Cu to the carbon atom, which accelerates the selection from *CHCOH to generate *CHCHOH, resulting in the high selectivity of ethanol. This work indicates a promising strategy in the rational design of asymmetrically coordinated single, dual, or tri-atom catalysts and provides a candidate material for CO2RR to produce ethanol.

Atomic Design of Copper Active Sites in Pristine Metal-Organic Coordination Compounds for Electrocatalytic Carbon Dioxide Reduction

Electrocatalytic carbon dioxide reduction reaction (CO2RR) has emerged as a promising and sustainable approach to cut carbon emissions by converting greenhouse gas CO2 to value-added chemicals and fuels. Metal-organic coordination compounds, especially the copper (Cu)-based coordination compounds, which feature well-defined crystalline structures and designable metal active sites, have attracted much research attention in electrocatalytic CO2RR. Herein, the recent advances of electrochemical CO2RR on pristine Cu-based coordination compounds with different types of Cu active sites are reviewed. First, the general reaction pathways of electrocatalytic CO2RR on Cu-based coordination compounds are briefly introduced. Then the highly efficient conversion of CO2 on various kinds of Cu active sites (e.g., single-Cu site, dimeric-Cu site, multi-Cu site, and heterometallic site) is systematically discussed, along with the corresponding catalytic reaction mechanisms. Finally, some existing challenges and potential opportunities for this research direction are provided to guide the rational design of metal-organic coordination compounds for their practical application in electrochemical CO2RR.

In Situ Synthesis of Copper-Based Metal-Organic Frameworks with Ligand Defects for Electrochemical Reduction of CO2 into C2 Products

Electrochemical reduction of CO2 into high-value-added products is a potential approach to solving environmental problems but is limited by poor product selectivity and low efficiency. Metal-organic framework (MOF) materials have been considered one of the most promising catalysts, but their application is limited by complicated preparation processes, especially during the synthesis of organic ligands. In this work, a new three-dimensional Cu-MOF (JXUST-301) with high porosity was constructed based on the naphthalene diimide (NDI) ligand. Furthermore, JXUST-301 with ligand defects (JXUST-301D) originating from the missing NDI unit was synthesized via an in situ reaction. The presence of ligand defects endows JXUST-301D with a better CO2RR performance with a FEC2 of 56.7% and a jC2 of -162.4 mA cm-2. Mechanistic studies revealed that the hierarchical pore structure and amino sites are created from the absence of the NDI unit, which promotes the exposure of catalytically active sites and CO2 enrichment. Furthermore, the electronic structure of the Cu sites is modulated to upshift the d-band center, facilitating chemical adsorption and activation of key reaction intermediates. This work provides new insight into the in situ preparation of efficient Cu-MOF catalysts by introducing defects for the CO2RR.

High Fe-Loading Single-Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

The current single-atom catalysts (SACs) for medicine still suffer from the limited active site density. Here, we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron. The constructed iron SACs (h3-FNC) with a high metal loading of 6.27 wt% and an optimized adjacent Fe distance of ~ 4 Å exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects. Attractively, a "density effect" has been found at a high-enough metal doping amount, at which individual active sites become close enough to interact with each other and alter the electronic structure, resulting in significantly boosted intrinsic activity of single-atomic iron sites in h3-FNCs by 2.3 times compared to low- and medium-loading SACs. Consequently, the overall catalytic activity of h3-FNC is highly improved, with mass activity and metal mass-specific activity that are, respectively, 66 and 315 times higher than those of commercial Pt/C. In addition, h3-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion (O2·-) and glutathione (GSH) depletion. Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h3-FNCs in promoting wound healing. This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Regulating the Critical Intermediates of Dual-Atom Catalysts for CO2 Electroreduction

Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO2 reduction reaction (eCO2RR) with multiple electron transfers. Among electrocatalysts, dual-atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO2RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO2RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal-support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO2RR processes are discussed.

Atomically Dispersed Metal Catalysts for the Conversion of CO2 into High-Value C2+ Chemicals

The conversion of carbon dioxide (CO2) into value-added chemicals with two or more carbons (C2+) is a promising strategy that cannot only mitigate anthropogenic CO2 emissions but also reduce the excessive dependence on fossil feedstocks. In recent years, atomically dispersed metal catalysts (ADCs), including single-atom catalysts (SACs), dual-atom catalysts (DACs), and single-cluster catalysts (SCCs), emerged as attractive candidates for CO2 fixation reactions due to their unique properties, such as the maximum utilization of active sites, tunable electronic structure, the efficient elucidation of catalytic mechanism, etc. This review provides an overview of significant progress in the synthesis and characterization of ADCs utilized in photocatalytic, electrocatalytic, and thermocatalytic conversion of CO2 toward high-value C2+ compounds. To provide insights for designing efficient ADCs toward the C2+ chemical synthesis originating from CO2, the key factors that influence the catalytic activity and selectivity are highlighted. Finally, the relevant challenges and opportunities are discussed to inspire new ideas for the generation of CO2-based C2+ products over ADCs.

Metal-Organic Frameworks for Electrocatalytic CO2 Reduction: From Catalytic Site Design to Microenvironment Modulation

The electrochemical reduction of CO2 to high-value carbon-based chemicals provides a sustainable approach to achieving an artificial carbon cycle. In the decade, metal-organic frameworks (MOFs), a kind of porous crystalline porous materials featuring well-defined structures, large surface area, high porosity, diverse components, easy tailorability, and controllable morphology, have attracted considerable research attention, serving as electrocatalysts to drive CO2 reduction. In this review, the reaction mechanisms of electrochemical CO2 reduction and the structure/component advantages of MOFs meeting the requirements of electrocatalysts for CO2 reduction are analyzed. After that, the representative progress for the precise fabrication of MOF-based electrocatalysts for CO2 reduction, focusing on catalytic site design and microenvironment modulation, are systemically summarized. Furthermore, the emerging applications and promising research for more practical scenarios related to electrochemical CO2 conversion are specifically proposed. Finally, the remaining challenges and future outlook of MOFs for electrochemical CO2 reduction are further discussed.

Rational design of organic ligands for metal-organic frameworks as electrocatalysts for CO2 reduction

Electrocatalytic carbon dioxide (CO2) reduction to valuable chemical compounds is a sustainable technology with enormous potential to facilitate carbon neutrality by transforming intermittent energy sources into stable fuels. Among various electrocatalysts, metal-organic frameworks (MOFs) have garnered increasing attention for the electrochemical CO2 reduction reaction (CO2RR) owing to their structural diversity, large surface area, high porosity and tunable chemical properties. Ligands play a vital role in MOFs, which can regulate the electronic structure and chemical environment of metal centers of MOFs, thereby influencing the activity and selectivity of products. This feature article discusses the strategies for the rational design of ligands and their impact on the CO2RR performance of MOFs to establish a structure-performance relationship. Finally, critical challenges and potential opportunities for MOFs with different ligand types in the CO2RR are mentioned with the aim to inspire the targeted design of advanced MOF catalysts in the future to achieve efficient electrocatalytic CO2 conversion.

Metal-ligand dual-site single-atom nanozyme mimicking urate oxidase with high substrates specificity

In nature, coenzyme-independent oxidases have evolved in selective catalysis using isolated substrate-binding pockets. Single-atom nanozymes (SAzymes), an emerging type of non-protein artificial enzymes, are promising to simulate enzyme active centers, but owing to the lack of recognition sites, realizing substrate specificity is a formidable task. Here we report a metal-ligand dual-site SAzyme (Ni-DAB) that exhibited selectivity in uric acid (UA) oxidation. Ni-DAB mimics the dual-site catalytic mechanism of urate oxidase, in which the Ni metal center and the C atom in the ligand serve as the specific UA and O2 binding sites, respectively, characterized by synchrotron soft X-ray absorption spectroscopy, in situ near ambient pressure X-ray photoelectron spectroscopy, and isotope labeling. The theoretical calculations reveal the high catalytic specificity is derived from not only the delicate interaction between UA and the Ni center but also the complementary oxygen reduction at the beta C site in the ligand. As a potential application, a Ni-DAB-based biofuel cell using human urine is constructed. This work unlocks an approach of enzyme-like isolated dual sites in boosting the selectivity of non-protein artificial enzymes.

Computational screening of defective BC3-supported single-atom catalysts for electrochemical CO2 reduction

The electrochemical CO2 reduction reaction (eCO2RR) driven by renewable electricity offers a green and sustainable technology for synthesizing chemicals and managing global carbon balance. However, developing electrocatalysts with high activity and selectivity for producing C1 products (CO, HCOOH, CH3OH, and CH4) remains a daunting task. In this study, we conducted comprehensive first-principles calculations to investigate the eCO2RR mechanism using B-defective BC3-supported transition metal single-atom catalysts (TM@BC3 SACs). Initially, we evaluated the thermodynamic and electrochemical stability of the designed 26 TM@BC3 SACs by calculating the binding energy and dissolution potential of the anchored TM atoms. Subsequently, the selectivity of the eCO2RR and hydrogen evolution reaction (HER) on stable SACs was determined by comparing the free energy change (ΔG) for the first protonation of CO2 with the ΔG of *H formation. The stability and selectivity screening processes enabled us to narrow down the pool of SACs to the 14 promising ones. Finally, volcano plots for the eCO2RR towards different C1 products were established by using the adsorption energy descriptors of key intermediates, and three SACs were predicted to exhibit high activity and selectivity. The limiting potentials (UL) for HCOOH production on Pd@BC3 and Ag@BC3 are -0.11 V and -0.14 V. CH4 is a preferred product on Re@BC3 with UL of -0.22 V. Elaborate electronic structure calculations elucidate that the activity and selectivity originate from the sufficient activation of the C-O bond and the strong orbital hybridization between crucial intermediates and metal atoms. The proposed catalyst screening criteria, constructed volcano plots and predicted SACs may provide a theoretical foundation for the development of computationally guided catalyst designs for electrochemical CO2 conversion to C1 products.

Construction of Two-Dimensional Organometallic Coordination Networks with Both Organic Kagome and Semiregular Metal Lattices on Au(111)

Two-dimensional metal-organic networks (2D MONs) having heterogeneous coordination nodes (HCNs) could exhibit excellent performance in catalysis and optoelectronics because of the unbalanced electron distribution of the coordinating metals. Therefore, the design and construction of 2D MONs with HCNs are highly desirable but remain challenging. Here, we report the construction of 2D organometallic coordination networks with an organic Kagome lattice and a semiregular metal lattice on Au(111) via the in situ formation of HCNs. Using a bifunctional precursor 1,4-dibromo-2,5-diisocyanobenzene, the coordination of isocyano with Au adatom on a room-temperature Au(111) yielded metal-organic coordination chains with isocyano-Au-isocyano nodes. In contrast, on a high-temperature Au(111), a selective debromination/coordination cascade reaction occurred, affording 2D organometallic coordination networks with phenyl-Au-isocyano nodes. By combining scanning tunneling microscopy and density functional theory calculations, we determined the structures of coordination products and the nature of coordination nodes, demonstrating a thermodynamically favorable pathway for forming the phenyl-Au-isocyano nodes.

Hydrophobic SiO2 Armor: Stabilizing Cuδ+ to Enhance CO2 Electroreduction toward C2+ Products in Strong Acidic Environments

Electroreduction of CO2 in highly acidic environments holds promise for enhancing CO2 utilization efficiency. Due to the HER interference and structural instability, however, challenges in improving the selectivity and stability toward multicarbon (C2+) products remain. In this study, we proposed an "armor protection" strategy involving the deposition of ultrathin, hydrophobic SiO2 onto the Cu surface (Cu/SiO2) through a simple one-step hydrolysis. Our results confirmed the effective inhibition of HER by a hydrophobic SiO2 layer, leading to a high Faradaic efficiency (FE) of up to 76.9% for C2+ products at a current density of 900 mA cm-2 under a strongly acidic condition with a pH of 1. The observed high performance surpassed the reported performance for most previously studied Cu-based catalysts in acidic CO2RR systems. Furthermore, the ultrathin hydrophobic SiO2 shell was demonstrated to effectively prevent the structural reconstruction of Cu and preserve the oxidation state of Cuδ+ active sites during CO2RR. Additionally, it hindered the accumulation of K+ ions on the catalyst surface and diffusion of in situ generated OH- ions away from the electrode, thereby favoring C2+ product generation. In situ Raman analyses coupled with DFT simulations further elucidated that the SiO2 shell proficiently modulated *CO adsorption behavior on the Cu/SiO2 catalyst by reducing *CO adsorption energy, facilitating the C-C coupling. This work offers a compelling strategy for rationally designing and exploiting highly stable and active Cu-based catalysts for CO2RR in highly acidic environments.

In Situ Reconstruction of Scalable Amorphous Indium-Based Metal-Organic Framework for CO2 Electroreduction to Formate over an Ultrawide Potential Window

Amorphous metal-organic frameworks (aMOFs) are highly attractive for electrocatalytic applications due to their exceptional conductivity and abundant defect sites, but harsh preparation conditions of "top-down" strategy have hindered their widespread use. Herein, the scalable production of aMIL-68(In)-NH2 was successfully achieved through a facile "bottom-up" strategy involving ligand competition with 2-methylimidazole. Multiple in situ and ex situ characterizations reveal that aMIL-68(In)-NH2 evolutes into In/In2O3-x as the genuine active sites during the CO2 electrocatalytic reduction (CO2RR) process. Moreover, the retained amino groups could enhance the CO2 adsorption. As expected, the reconstructed catalyst demonstrates high formate Faradaic efficiency values (>90%) over a wide potential range of 800 mV in a flow cell, surpassing most top-ranking electrocatalysts. Density functional theory calculations reveal that the abundant oxygen vacancies in aMIL-68(In)-NH2 induce more local charges around electroactive sites, thereby promoting the formation of HCOO* intermediates. Furthermore, 16 g of samples can be readily prepared in one batch and exhibit almost identical CO2RR performances. This work offers a feasible batch-scale strategy to design amorphous MOFs for the highly efficient electrolytic CO2RR.

Enhancing CO2 Electroreduction to C2 Products on Metal-Nitrogen Sites by Regulating H2O Dissociation

Water dissociation remarkably affects the CO2 reduction to CO and HCOOH, but whether it is effective for two-carbon product formation on M-Nx-containing catalysts is still ambiguous. Herein, by using a fluorinated metal phthalocyanine (MPc-F) as the M-N4-based model electrocatalyst, experimental and theoretical results reveal that the H2O-dissociation-induced active H species decrease the overpotential of the *CO hydrogenation to *CHO and facilitate the C-C coupling between *CHO and neighboring CO. Such an effect is strengthened by an increase in the *CO binding strength on the metal center. By introducing CuPc as the H2O dissociation catalyst into MPc-F (MPc-F/CuPc) to accurately regulate the H2O dissociation, the faradic efficiency of C2 products on FePc-F/CuPc and MnPc-F/CuPc increases from 0% (FePc-F and MnPc-F) to 26 and 36%, respectively. This work develops a novel strategy for enhancing the selectivity of M-Nx-containing catalysts to C2 products and reveals the correlation between H2O dissociation and C2 product formation.

Customizing catalyst surface/interface structures for electrochemical CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) provides a promising route to converting CO2 into value-added chemicals and to neutralizing the greenhouse gas emission. For the industrial application of CO2RR, high-performance electrocatalysts featuring high activities and selectivities are essential. It has been demonstrated that customizing the catalyst surface/interface structures allows for high-precision control over the microenvironment for catalysis as well as the adsorption/desorption behaviors of key reaction intermediates in CO2RR, thereby elevating the activity, selectivity and stability of the electrocatalysts. In this paper, we review the progress in customizing the surface/interface structures for CO2RR electrocatalysts (including atomic-site catalysts, metal catalysts, and metal/oxide catalysts). From the perspectives of coordination engineering, atomic interface design, surface modification, and hetero-interface construction, we delineate the resulting specific alterations in surface/interface structures, and their effect on the CO2RR process. At the end of this review, we present a brief discussion and outlook on the current challenges and future directions for achieving high-efficiency CO2RR via surface/interface engineering.