Redox-pathway steering enables photocatalytic valorization of CO₂ and 1-phenylethanol with record quantum efficiency

Integrating photocatalytic CO₂ reduction with oxidative organic synthesis constructs a promising policy for maximizing charge carrier utilization. Herein, highly efficient photoredox catalysis of CO₂ reduction to CO (467.1 μmol h^-1) and H₂ (78.4 μmol h^-1), coupled with 1-phenylethanol oxidation to pinacol (553.9 μmol h^-1) is attained over diethylenetriamine modified CdS, delivering a record-high apparent quantum efficiency of 25%, 100% pinacol selectivity, and a unity reaction stoichiometry. The amine groups effectively modulate both the reductive and oxidative pathways by enhancing CO₂ capture and activation and stabilizing carbon-centered radicals, respectively. Also, they prompt charge carrier separation and transfer by forming strong Cd-N bonds with CdS. Mechanistic studies reveal that excited holes drive 1-phenylethanol oxidation to pinacol via carbon radical dimerization, while donating protons to boost CO₂-to-CO reduction via sequential proton-assisted electron transfer processes. This work lights up the route for building advanced artificial photosynthetic systems through precise surface engineering with functional organic groups.