Photocatalytic　reduction　of　CO2　with　H2O　is　thought　as　an　environment　friendly　approach　for　sustainable　development.　It　is　highly　desirable　but　remains　challenging　to　develop　photocatalyst　with　metal-free　site　for　CO2　reduction.　Here,　we　fabricated　a　heterostructure　by　integrating　azine-based　COF　with　ZnIn2S4,　where　the　azine　unit　in　COF　acts　as　metal-free　sites　for　CO2　adsorption　and　reduction.　The　as-formed　interfused　heterointerface　in　the　heterostructure　ensures　the　effective　electron　transfer　from　ZnIn2S4　across　the　interface　to　the　COF,　resulting　in　a　spatial　separation　of　redox　sites　for　CO2　reduction　and　water　oxidation.　The　hybrid　catalyst　exhibits　remarkably　enhanced　photocatalytic　activity　for　CO2　reduction　to　CO,　which　is　8　and　6　times　than　the　COF　and　ZnIn2S4,　respectively,　and　is　even　comparable　with　some　metal-catalyzed　CO2　reduction　systems.　This　study　provides　a　new　paradigm　to　mimic　natural　photosynthesis　by　using　metal-free　site　for　CO2　reduction.　©　2024　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.