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.