Surface-iodination-induced efficient charge separation in bismuth oxysulfide crystals for enhanced photocatalytic CO2 conversion

•Surface iodinated Bi2O2S were prepared as inspired [Bi2O2]2+-containing materials.•Surface iodide ions facilitated the separation of photo-generated carriers in IBOS.•2.0%IBOS exhibited superb abilities for the adsorption and activation toward CO2.•The CH4 yield of 80.03 μmol g−1 was achieved by visible light-driven CO2 photoreduction.•The reaction mechanism was unveiled by experimental and theoretical analyses.