Metal-organic framework-based single-atom catalysts for efficient electrocatalytic CO₂ reduction reactions

Metal-organic framework (MOF) based single-atom catalysts (SACs) with distinctive features are emerging extraordinary materials in the electrochemical field in the latest years. MOF has the virtues of functional tunability, high surface areas, and well-defined pores structures, while SAC possesses the advantages of maximum atom utilization, special electronic characteristics, and quantum size effects. By combining the merits of both, MOF-based SACs exhibit huge potential in electrocatalytic CO₂ reduction reactions (CO₂RR) and, more generally, in the field of electroreduction reactions. In this review, the diverse fabrication strategies and principles of MOF-based SACs, including MOF-immobilized SACs and MOF-derived SACs, and the corresponding representative samples of each strategy are systematically introduced and summarized. Then, insights into the mechanisms and pathways of electrochemical CO₂RR are discussed. In addition, we illustrate elaborately the recent progress of MOF-derived SACs for electrocatalytic CO₂RR to valuable chemicals/fuels according to the classification of catalytic products, C₁, C₂, and C₂₊ species. At last, the current challenges and future development directions of MOF-based SACs toward electrochemical CO₂RR are proposed. We hope that this review would be helpful in rational designing MOF-based SACs with higher efficiency, selectivity, and long-term durability for the electrocatalytic CO₂RR and/or a wider range of electrochemical applications in the future.