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

The direct photocatalytic conversion of CO₂ and H₂O into high-value C₃ chemicals holds great promise but remains challenging due to the intrinsic difficulty of C₁–C₁ and C₂–C₁ 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 C₃ intermediates, including ^*COCOHCO, ^*OCCCO, and ^*CHCHCO, are identified, providing a clear reaction pathway for CO₂ to CH₃CH₂COOH conversion. The Cu-ZnS photocatalyst achieves a CO₂ to CH₃CH₂COOH 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 CO₂ into C₃ products, paving the way for future advancements in sustainable chemical synthesis.