Covalent　organic　frameworks　(COFs)　are　crystalline　porous　materials　with　enormous　potential　for　realizing　solar-driven　CO2-to-fuel　conversion,　yet　the　sluggish　transfer/separation　of　photoinduced　electrons　and　holes　remains　a　compelling　challenge.　Herein,　a　step　(S)-scheme　heterojunction　photocatalyst　(CuWO4-COF)　was　rationally　fabricated　by　a　thermal　annealing　method　for　boosting　CO2　conversion　to　CO.　The　optimal　CuWO4/COF　composite　sample,　integrating　10　wt%　CuWO4　with　an　olefin　(C═C)　linked　COF　(TTCOF),　achieved　a　remarkable　gas–solid　phase　CO　yield　as　high　as　7.17　±　0.35　μmol　g−1h−1　under　visible　light　irradiation,　which　was　significantly　higher　than　the　pure　COF　(1.6　±　0.29　μmol　g−1h−1).　The　enhanced　CO2　conversion　rate　could　be　attributable　to　the　interface　engineering　effect　and　the　formation　of　internal　electric　field　(IEF)　directing　from　TTCOF　to　CuWO4　according　to　the　theoretical　calculation　and　experimental　results,　which　also　proves　the　electrons　transfer　from　TTCOF　to　CuWO4　upon　hybridization.　In　addition,　driven　by　the　IEF,　the　photoinduced　electrons　can　be　steered　from　CuWO4　to　TTCOF　under　visible　light　irradiation　as　well-elucidated　by　in-situ　irradiated　X-ray　photoelectron　spectroscopy,　verifying　the　S-scheme　charge　transfer　pathway　over　CuWO4/COF　composite　heterojunctions,　which　greatly　foster　the　photoreduction　activity　of　CO2.　The　preparation　technique　of　the　S-scheme　heterojunction　photocatalyst　in　this　study　provides　a　paradigmatic　protocol　for　photocatalytic　solar　fuel　generation.　©　2023　Elsevier　Inc.