Boosting Electrochemical CO2 Reduction on Copper‐Based Metal‐Organic Frameworks via Valence and Coordination Environment Modulation

Abstract Cu‐based metal‐organic frameworks (MOFs) have attracted much attention for electrocatalytic CO 2 reduction to high value‐added chemicals, but they still suffer from low selectivity and instability. Here, an associative design strategy for the valence and coordination environment of the metal node in Cu‐based MOFs is employed to regulate the CO2 electroreduction to ethylene. A novel “reduction‐cleavage‐recrystallization” method is developed to modulate the Cu(II)‐Trimesic acid (BTC) framework to form a Cu(I)‐BTC structure enriched with free carboxyl groups in the secondary coordination environment (SCE). In contrast to Cu(II)‐BTC, the Cu(I)‐BTC shows higher catalytic activity and better ethylene selectivity (≈2.2‐fold) for CO 2 electroreduction, which is further enhanced by increasing the content of free carboxyl groups, resulting in ethylene Faraday efficiency of up to 57% and the durability of the catalyst could last for 38 h without performance decline. It indicates that the synergistic effect between Cu(I)‐O coordinated structure and free carboxyl groups considerably enhances the dimerization of *CO intermediates and hinders the hydrogenation of *CO intermediates in these competitive pathways. This work unravels the strong dependence of CO 2 electroreduction on the Cu valence state and coordination environment in MOFs and provides a platform for designing highly selective electrocatalytic CO 2 reduction catalysts.