Coherent single-atom and vacancy dual-functional sites enable efficient solar-driven co-production of H2 and value-added chemicals with 100% selectivity.

Semiconductor-mediated photoreforming is promising for concurrent H2 and value-added chemical production but suffers from rapid charge recombination and slow reaction kinetics. Herein, we construct an ultrathin porous CdS nanosheet co-modified with atomically dispersed Ru and S vacancies, which synergistically promotes the photocatalytic dehydrogenation of ethanol to H2 and acetaldehyde, with subsequent acid-catalyzed condensation yielding 1,1-diethoxyethane (DEE) at 100% overall selectivity. We demonstrate that Ru single atoms extract photogenerated electrons, while S vacancies localize holes, markedly enhancing bulk carrier separation and migration. Beyond spatial charge separation, operando studies further reveal that these dual sites cooperatively strengthen the oxidation state of adjacent S atoms, facilitating charge injection into the key C2H5O* intermediate and reducing the dehydrogenation barrier. The optimized catalyst achieves an H2 evolution rate of 157.9 μmol h-1, 81.5 times that of pristine CdS, along with full selectivity for DEE. This system also demonstrates generality in lactic acid photoreforming, yielding a 27.3-fold enhancement in H2 evolution and 93.3% pyruvic acid selectivity. This work provides a fundamental mechanistic insight into steering photoreforming reaction via atomic-site engineering for solar-to-chemical conversion.