Cu‐ZnS Modulated Multi‐Carbon Coupling Enables High Selectivity Photoreduction CO2 to CH3CH2COOH

Abstract The direct photocatalytic conversion of CO 2 and H 2 O into high‐value C 3 chemicals holds great promise but remains challenging due to the intrinsic difficulty of C 1 –C 1 and C 2 –C 1 coupling processes and the lack of clarity regarding the underlying reaction mechanisms. Here, the design and synthesis of a Cu‐ZnS photocatalyst featuring dispersed Cu single atoms are reported. These Cu single atoms are coordinated with S atoms, forming unique Cu‐S‐Zn active units with tunable charge distributions that interact favorably with surface‐adsorbed intermediates. This configuration stabilizes the * COHCO intermediate and facilitates its subsequent coupling with * CO to form * COCOHCO both thermodynamically and kinetically favorable on the Cu‐ZnS surface. Notably, multiple critical C 3 intermediates, including * COCOHCO, * OCCCO, and * CHCHCO, are identified, providing a clear reaction pathway for CO 2 to CH 3 CH 2 COOH conversion. The Cu‐ZnS photocatalyst achieves a CO 2 to CH 3 CH 2 COOH conversion rate of 0.45 µmol h − ¹ with an electron selectivity of 91.2%. Remarkably, in the presence of triethanolamine, the production rate increases to 16.9 µmol h − ¹ with a selectivity of 99.8%. These findings underscore the importance of modulating multicarbon coupling processes to enable the efficient photocatalytic transformation of CO 2 into C 3 products, paving the way for future advancements in sustainable chemical synthesis.