Asymmetric Bi and S Single Atoms Over Porous Single-Crystal TiO₂ for Efficient CO₂ Photoreduction to Acetic Acid

Regulating multi-step photocatalytic conversion of molecules remains challenging, primarily due to the complex interplays among light absorption, reactant binding, and charge separation and transfer processes. Here, the photocatalytic conversion of CO₂ to acetic acid is effectively achieved via the triadic synergy of asymmetric Bi (Bi–O₄), S (S–O₂), and 3D porous single-crystal TiO₂, which is realized through a selective extraction process. Specifically, Bi active sites lower the energy barrier for CHO^* generation and C─C coupling; meanwhile, the S─O structure modulates Bi─O and Ti─O configurations to form strong Lewis base site ((SO_2–BiO₄)^δ−) by constructing a surface sulfate species, thereby accelerating the hydrogenation step in CO₂ reduction. The specifically designed photocatalytic system achieves a high acetic acid production rate of 66.7 µmol g⁻¹ h⁻¹ with over 89% selectivity. This design underscores the significance of engineering synergistic active sites and charge transfer to enhance photocatalytic conversion efficiency, offering valuable insight into the structure-activity relationship for developing high-performance photocatalysts. © 2026 The Author(s). Advanced Materials published by Wiley-VCH GmbH.