Promoting Interfacial Electron Transfer by In Situ Generated Asymmetric Sn–O_v–Bi Sites for Selective CO₂ Photoreduction

Photocatalytic CO2 reduction offers a promising pathway for carbon neutrality, which fundamentally depends on the transfer of photoexcited electrons to the symmetric O═C═O bonds. However, precisely adjusting the electronic structure of active sites to promote the activation of the CO2 molecules is still challenging. Herein, we demonstrate a light-driven engineering strategy for in situ construction of a dynamic active site, where the strain-induced asymmetric Sn–O–Bi units could evolve into self-optimized Sn–Ov–Bi triatomic sites under irradiation. These in situ generated photosensitive Ovs increase the electron density of neighboring Sn atoms and adjacent Bi atoms to form unique Sn–Ov–Bi triatomic sites, creating a polarized built-in electric field (IEF) that can accelerate charge separation and transfer. In situ electron paramagnetic resonance spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy further reveal that the strong electron transfer between the Sn–Ov–Bi sites and reactant molecules highly promotes the activation of the CO2 molecules and the formation of H* species, thus facilitating the generation of critical COOH* intermediates. As a result, the in situ-generated asymmetric Sn–Ov–Bi sites enable BiOBr to achieve a stable and high CO production rate with 100% selectivity. This work provides a paradigm for the structural design of dynamic asymmetric active sites and highlights the importance of in situ electronic manipulation in a catalytic reaction.