Asymmetric Triple‐Atom Sites Combined with Oxygen Vacancy for Selective Photocatalytic Conversion of CO ₂ to Propionic Acid

Abstract Photocatalytic CO 2 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 δ+ ‐W δ+ ) on CuWO 4 with oxygen vacancies (OVs) (named CWO‐OVs). The optimized CWO‐OVs achieve a photochemical synthesis rate of propionic acid (C 3 H 6 O 2 , PA) of 86.46±2.92 μmol g −1 h −1 , with an electron‐based selectivity of 89.27 %, which exhibits a remarkable advantage in the field of photocatalytic CO 2 reduction to C 2+ 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 δ+ triggers the first step of C 1 ‐C 1 coupling to form *CH 2 CH 3 ; (2) Cu δ+ ‐W δ+ facilitates subsequent C 2 ‐C 1 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.