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

Abstract

The electrocatalytic CO 2 reduction reaction (CO 2 RR) to produce multicarbon (C 2+ ) products such as ethylene (C 2 H 4 ) is a promising method to achieve carbon neutrality, but it is very difficult due to the high activation barrier of CO 2 and the low selectivity of the CO 2 RR especially for C 2+ 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 CO 2 to C 2 H 4 with a high faradaic efficiency (FE) (70.9%) with the current density of 20.4 mA·cm –2 . When the H-cell was replaced by a flow cell, the current density could be increased to 161 mA·cm –2 with a still high FE of C 2 H 4 (66.9%). Mechanism studies suggested that in the Cu-SAs@Ir-PCN-222-PA-catalyzed CO 2 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 C 2+ product C 2 H 4 . This work offers a new kind of MOF electrocatalysts with dual active sites to drive CO 2 reduction to generate C 2+ products.