Photocatalytic　conversion　of　CO2　into　valued　chemicals　has　evoked　broad　interest.　However,　the　photocatalytic　efficiency　is　limited　by　the　adsorption　and　activation　capability　of　the　catalyst　surface　for　CO2.　Here,　isomor-phically　Sn　(IV)　doped　BiOBr　is　achieved　through　a　facile　chemical　method.　The　as-prepared　Sn-doped　BiOBr　demonstrates　the　enhanced　performance　of　photocatalytic　CO2　reduction　into　CO.　Thereinto,　the　4Sn-BiOBr　sample　shows　the　best　activity　with　the　CO　yield　of　165.6　mu　mol　center　dot　g-　1　center　dot　h-1,　which　is　7.8　times　higher　than　that　of　pristine　BiOBr.　Sn　ions　and　oxygen　vacancies　(OVs)　are　shown　to　be　simultaneously　introduced　into　the　crystal　lattice　of　BiOBr.　As　a　result,　surface　frustrated　Lewis　acidic　sites　and　Lewis　basic　sites　of　BiOBr　are　constructed　and　the　activation　capability　for　CO2　is　improved　obviously.　This　work　presents　the　feasible　tunability　of　catalytic　active　sites　for　catalyst　at　atom-scale,　and　offers　fundamental　insights　for　understanding　of　the　mechanism　of　photocatalytic　CO2　reduction.