Guiwei He, Zihao Jiao, Yuting Yin, Fang Wang, Shengjie Bai, Ya Liu, Lei Guo
ABSTRACT Solar‐driven conversion of CO 2 and H 2 O into propionic acid remains challenging due to the complexity of multi‐electron transfer processes. Here, we couple frustrated Lewis pairs (FLPs), surface hydroxyls, and thermal excitation to build an electron‐rich Cu microenvironment for CO 2 ‐to‐propionic acid conversion. In the In(OH) 3 /CuO x @CF catalyst, oxygen vacancies (O v ) and neighboring Cu centers form O v ─Cu FLPs, while adjacent ─OH groups serve as cooperative Lewis bases and proton reservoirs. This architecture funnels photogenerated electrons from In(OH) 3 to Cu, stabilizes Cu δ+ (0 < δ <1) species, and markedly enhances interfacial electron localization. This electron‐rich environment lowers the activation barrier for CO 2 activation, stabilizes key intermediates (*COH, *CHCO, *CH 2 COCO), and promotes sequential *CO─*COH and *CHCO─*CO coupling. Thermal further reinforces localization, accelerates interfacial charge transfer, and decreases the energy barrier of the rate‐determining step, further accelerating C─C coupling. Propionic acid is achieved at a rate of 22711 µmol h −1 m −2 with 99% selectivity, yielding a solar‐to‐propionic acid efficiency of 0.15%, without sacrificial agents. This work highlights the crucial role of interfacial electron localization in multi‐electron transfer and C─C coupling, and provides general design principles for photothermal CO 2 reduction to higher‐order oxygenates.