Photocatalytic　CO2　reduction　comprises　two　coupled　half-reactions:　CO2　reduction　and　H2O　oxidation.　Efficient　coupling　of　these　reactions　maximizes　the　utilization　of　photogenerated　electrons　and　holes,　enhancing　CO2　conversion　and　product　selectivity.　In　this　study,　sulfur-deficient　VS-Zn3In2S6　(VS-ZIS)　catalysts　were　synthesized　via　an　ethylene　glycol　solvothermal　method,　followed　by　anchoring　Fe　single-atom　sites　(Fe/VS-ZIS)　to　facilitate　CO2　photoreduction　using　H2O　as　proton　source.　The　1　%Fe/VS-ZIS　exhibited　exceptional　performance,　with　a　CO　production　rate　of　88.6　μmol·g−1·h−1　and　97　%　selectivity.　Experimental　and　DFT　results　revealed　that　VS　functioned　as　reductive　sites　to　strengthen　CO2　adsorption　and　activation,　while　Fe　single　atoms　(SAs)　served　as　oxidative　sites　to　facilitate　H2O　dissociation　for　proton　supply.　Fe　SAs　also　induced　spin　polarization　to　enhance　IEF,　thereby　suppressing　photogenerated　charges　recombination　at　redox　sites.　Meanwhile,　Fe　SAs　reduced　COOH*　formation　energy　barrier　and　lowered　CO　desorption　temperature,　improving　CO　selectivity.　The　constructed　dual　active　sites　synergistically　enhanced　the　overall　photocatalytic　CO2　reduction　performance.　This　work　offers　new　technical　pathways　for　designing　redox　dual-active　sites　to　boost　the　overall　photocatalytic　CO2　reduction　efficiency.　©　2025　Elsevier　B.V.