Charge　transfer　efficiency　between　discrete　photosensitizers　and　catalytic　sites　is　a　key　limiting　factor　in　artificial　photosynthesis.　It　is　highly　desirable　but　challenging　to　efficiently　combine　the　two　sections　into　an　integration　system　and　get　insight　into　the　kinetics　and　mechanisms.　Here　in,　the　photosensitizer　[Ru(bpy)3]2+　(bpy　=　2,2′-bipyridine)　and　active　cobalt　porphyrin　(Co-Por)　sites　were　integrated　into　a　covalent　organic　framework　(COF),　named　COF-RuBpy-Co,　for　efficient　charge　transfer　and　photocatalytic　CO2　reduction.　The　catalyst　COF-RuBpy-Co　exhibited　excellent　CO2　photoreduction　activity　towards　CO　production　with　a　rate　of　547　μmol　g−1h−1,　which　is　1.4-fold　enhancement　over　the　physical　mixture　of　Ru(bpy)3Cl2　and　COF-Bpy-Co.　In　situ　X-ray　photoelectron　spectroscopy　combined　with　theoretical　calculation　results　revealed　that　COF-RuBpy-Co　achieved　efficient　photoelectron　transfer　from　[Ru(bpy)3]2+　to　cobalt　porphyrin.　More　importantly,　transient　absorption　spectroscopy　indicated　that　the　covalent　linking　[Ru(bpy)3]2+and　Co-Por　units　realized　a　faster　charge　transfer　(44.2　ps)　over　the　large　π-conjugated　system.　This　work　provides　vital　insights　into　the　charge　carrier　transfer　process　and　demonstrates　the　potential　of　COFs　as　a　platform　in　artificial　photosynthesis.　©　2023　Elsevier　B.V.