AbstractUnraveling atomic‐level active sites of layered photocatalyst towards low‐concentration CO₂ conversion is still challenging. Herein, the yield and selectivity of photocatalytic CO₂ reduction of the Aurivillius‐related oxide semiconductor Bi₂O₂SiO₃ nanosheet (BOSO) were largely improved using a surface sulfidation strategy. The experiment and theoretical calculation confirmed that surface sulfidation of the Bi₂O₂SiO₃ nanosheet (S‐BOSO, 6.28 nm) redistributed the charge‐enriched Bi sites, extended the solar spectrum absorption to the whole visible range, and considerably enhanced the charge separation, in addition to creating new reaction active sites, as compared to pristine BOSO. Subsequently, surface sulfidation played a switchable role, wherein S‐BOSO showed a very high CH₃OH generation rate (12.78 µmol g⁻¹ for 4 h, 78.6% selectivity) from low‐concentration CO₂ (1000 ppm) under visible light irradiation, which outperforms most of the state‐of‐the‐art photocatalysts under similar conditions. This study presents an atomic‐level modification protocol for engineering reactive sites and charge behaviors to promote solar‐to‐energy conversion.