Highly Ethylene-Selective Electrocatalytic CO₂ Reduction Enabled by Isolated Cu−S Motifs in Metal–Organic Framework Based Precatalysts

Copper-based materials are efficient electrocatalysts for the conversion of CO₂ to C₂₊ products, and most these materials are reconstructed in situ to regenerate active species. It is a challenge to precisely design precatalysts to obtain active sites for the CO₂ reduction reaction (CO₂RR). Herein, we develop a strategy based on local sulfur doping of a Cu-based metal–organic framework precatalyst, in which the stable Cu−S motif is dispersed in the framework of HKUST-1 (S-HKUST-1). The precatalyst exhibits a high ethylene selectivity in an H-type cell with a maximum faradaic efficiency (FE) of 60.0 %, and delivers a current density of 400 mA cm⁻² with an ethylene FE up to 57.2 % in a flow cell. Operando X-ray absorption results demonstrate that Cu^δ+ species stabilized by the Cu−S motif exist in S-HKUST-1 during CO₂RR. Density functional theory calculations indicate the partially oxidized Cu^δ+ at the Cu/Cu_xS_y interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimized adsorption energy.