Nitrogen-Bridged S-N-Cu Sites for CO₂ Photoreduction to Ethanol with 99.5 % Selectivity in Pure Water

Solar-driven CO₂ reduction to ethanol is extremely challenging due to the limited efficiency of charge separation, sluggish kinetics of C-C coupling, and unfavorable formation of oxygenate intermediates. Here, we elaborately design a red polymer carbon nitride (RPCN) consisting of S-N and Cu-N₄ dual active sites (Cu/S-RPCN) to address this challenge, which achieves an impressive ethanol evolution rate of 50.4 μmol g^-1 h^-1 with 99.5 % selectivity for CO₂ photoreduction in pure water. Cu and S atoms within the Cu-N-S configuration can serve as trapping centers for electrons and holes, respectively, providing spatial separation for photogenerated charge carriers. The incorporation of S atoms optimizes the adsorption of *CO on Cu atoms and reduces the energy barrier for the formation of *CO-COH intermediate. The adsorption strength of *OCHCH₂OH intermediate on the Cu atoms via the O-Cu-C configuration can affect the selectivity of the C₂ products as the cleavage of the Cu-O/Cu-C bonds determines the ethanol/ethylene pathway. The S-N-Cu structure weakens the Cu-O bond, thereby promoting the production of ethanol. This work provides a novel approach to fine-tune the surrounding microenvironment of metal atoms on carbon nitride for highly effective photocatalytic conversion of CO₂ to ethanol.