Defect　engineering　is　a　highly　effective　approach　to　regulate　the　electronic　structure　of　the　catalyst　surface,　widely　employed　in　the　field　of　photocatalytic　energy　conversion.　In　this　study,　we　have　successfully　synthesized　a　novel　dual-defective　In2S3/Zn0.3Cd0.7S　(IS/ZCS)　heterojunction　structure　via　a　self-assembly　method,　composed　of　Zn-vacancy-rich　Zn0.3Cd0.7S　(ZCS)　and　S-vacancy-rich　In2S3　(IS).　Under　visible　light　illumination,　3%　IS/ZCS　sample　exhibits　remarkable　photocatalytic　performance　in　the　synergistic　reaction　of　CO2　reduction　and　4-chlorobenzyl　alcohol　(Cl-PhCH2OH)　oxidation　with　the　CO　yield　significantly　improved　by　a　factor　of　3.5　and　51　compared　to　that　of　ZCS　and　IS,　respectively.　The　combined　experimental　data　and　theoretical　calculations　demonstrate　that　the　dual-defective　structure　and　Z-scheme　transfer　mode　are　the　key　factors　behind　the　enhanced　photocatalytic　activity,　providing　more　active　sites　and　effectively　improving　the　utilization　of　photogenerated　charge　carriers　(PCCs).　Moreover,　the　reaction　pathway　and　catalytic　mechanism　of　photocatalytic　CO2　reduction　were　elucidated　by　the　in-situ　FTIR　technique　combined　with　DFT　calculations,　monitoring　the　intermediate　and　final　products　during　the　reaction　period.　Our　results　provide　a　powerful　example　of　designing　novel　heterojunction　photocatalysts　with　high　activity　and　accelerating　the　separation　of　PCCs,　with　broad　implications　for　the　development　of　efficient　photocatalytic　systems.　©　2023　Elsevier　B.V.