Exploring　high-efficiency　photocatalysts　for　CO2　reduction　is　highly　desirable　in　view　of　the　current　energy　and　environmental　crisis.　Herein,　we　present　the　design　and　synthesis　of　branch-like　ZnS-DETA/CdS　(DETA　=　diethylenetriamine)　hierarchical　heterostructures　assembled　from　ultrathin　nanowires　for　efficient　photocatalytic　CO2　reduction　under　visible　light.　With　ZnS-DETA　nanosheets　as　a　precursor,　the　ZnS-DETA/CdS　hierarchical　hybrids　are　readily　achieved　through　a　cation-exchange　approach,　leading　to　the　formation　of　uniformly　distributed　heterojunctions　in　nanodomains　and　controllable　compositions.　The　systematic　physicochemical　characterizations　reveal　that　the　ZnS-DETA/CdS　heterostructures　can　effectively　absorb　the　visible　light,　offer　large　surface　area　and　abundant　active　sites　for　CO2　adsorption　and　surface　reactions,　and　expedite　separation　and　transport　of　charge　carriers.　The　ZnS-DETA/CdS　photocatalyst　shows　the　highest　CO　generation　rate　of　33.3　μmol　h-1　(i.e.,　8325　μmol　h-1　g-1)　for　deoxygenative　CO2　reduction.　Moreover,　the　photocatalyst　also　exhibits　high　stability　and　good　reusability　for　the　CO2　reduction　reaction.　In　addition,　a　possible　photocatalytic　CO2　reduction　mechanism　over　the　ZnS-DETA/CdS　heterostructure　is　proposed.　©　2019　The　Royal　Society　of　Chemistry.