Engineering Dual Sites into the Confined Nanospace of the Porphyrinic Metal-Organic Framework for Tandem Transformation of CO₂ to Ethylene

The electrocatalytic CO2 reduction reaction (CO2RR) to produce multicarbon (C2+) products such as ethylene (C2H4) is a promising method to achieve carbon neutrality, but it is very difficult due to the high activation barrier of CO2 and the low selectivity of the CO2RR especially for C2+ products. Herein, copper single atoms (Cu-SAs) were confined into the nanospace of an iridium porphyrin-based metal-organic framework (Ir-PCN-222) to form the metal-organic framework (MOF) composite (Cu-SAs@Ir-PCN-222-PA) with dual active sites of Ir-porphyrin and Cu-SAs through the precoordination confinement strategy. Catalytic results disclosed that Cu-SAs@Ir-PCN-222-PA could drive the reduction of CO2 to C2H4 with a high faradaic efficiency (FE) (70.9%) with the current density of 20.4 mAcm(-2). When the H-cell was replaced by a flow cell, the current density could be increased to 161 mAcm(-2) with a still high FE of C2H4 (66.9%). Mechanism studies suggested that in the Cu-SAs@Ir-PCN-222-PA-catalyzed CO2 electroreduction reaction, CO was first generated on the Ir-porphyrin and then moved to the adsorbed *CO intermediate on the nearby Cu-SAs, and after that, the C-C coupling process was carried out on Cu-SAs to provide the C2+ product C2H4. This work offers a new kind of MOF electrocatalysts with dual active sites to drive CO2 reduction to generate C2+ products.