Converting　CO2　into　CO,　CH4,　and　other　hydrocarbons　using　solar　energy　presents　a　viable　approach　for　addressing　energy　shortages.　In　this　study,　photocatalysts　with　S-deficient　WO3/Zn3In2S6　(WO3/VS-ZIS)　S-scheme　heterojunctions　have　been　successfully　synthesized.　Under　UV–vis　light　irradiation,　20　%WO3/VS-ZIS　demonstrated　significantly　improved　CO2　reduction　activity　and　CH4　selectivity.　Detailed　characterization　and　density　functional　theory　(DFT)　calculations　reveal　that　the　enhanced　performance　is　due　to　the　synergistic　optimization　of　the　S-scheme　heterojunction　and　sulfur　vacancies　(VS)　for　CO2　reduction.　The　presence　of　VS　aids　in　the　adsorption　and　activation　of　CO2　and　enhances　the　separation　of　charge　carriers.　The　2D/2D　S-scheme　heterostructure　assembled　with　WO3　nanosheets　not　only　accelerates　the　migration　and　separation　of　photoexcited　charge　carriers　but　also　improves　the　adsorption　of　H2O　and　the　formation　of　VS,　thereby　increasing　the　adsorption　and　activation　of　CO2　and　facilitating　the　protonation　of　CO*　to　produce　CH4.　This　study　clarifies　the　synergistic　effect　of　VS　and　S-scheme　heterostructures　in　improving　photocatalytic　performance,　offering　valuable　insights　into　the　photoactivation　process　of　CO2　at　VS　in　S-scheme　heterojunctions.　©　2024　Elsevier　Inc.