Asymmetric Triple-Atom Sites Combined with Oxygen Vacancy for Selective Photocatalytic Conversion of CO to Propionic Acid.

Photocatalytic CO reduction to multicarbon products is an emerging approach for achieving carbon neutrality; however, the design of active sites that effectively promote multistep C-C coupling remains a challenge. Here, we propose a straightforward defect engineering approach to construct asymmetric triple-atom sites (Cu-Cu-W) on CuWO with oxygen vacancies (OVs) (named CWO-OVs). The optimized CWO-OVs achieve a photochemical synthesis rate of propionic acid (CHO, PA) of 86.46±2.92 μmol g h, with an electron-based selectivity of 89.27 %, which exhibits a remarkable advantage in the field of photocatalytic CO reduction to C products. Experimental results and density functional theory calculations corroborate the prominent role of OVs in inducing the triple-atom sites: (1) the asymmetric Cu-Cu triggers the first step of C-C coupling to form *CHCH; (2) Cu-W facilitates subsequent C-C bonding, ultimately leading to PA production. This charge-asymmetric cascade reaction system offers new insights into the design of efficient photocatalysts for the synthesis of multi-carbon products.