Owing　to　the　large　exciton　binding　energy(＞100　meV)of　most　organic　materials,the　process　of　exciton　dissociation　into　free　electrons　and　holes　is　seriously　hindered,which　plays　a　key　role　in　the　photocat-alytic　system.In　this　study,a　series　of　chalcogen(S,Se)-substituted　mesoporous　covalent　organic　frame-works(COFs)have　been　synthesized　for　enhanced　photocatalytic　organic　transformations.Photoelectro-chemical　measurements　indicate　that　the　introduction　of　semi-metallic　Se　atom　and　the　enlargement　of　conjugation　degree　can　not　only　reduce　the　exciton　binding　energy　accelerating　the　charge　separation,but　also　reduce　the　band　gap　of　COFs.As　a　result,the　COF-NUST-36　with　the　lowest　exciton　binding　energy(39.5　meV)shows　the　highest　photocatalytic　performance　for　selective　oxidation　of　amines(up　to　98％Conv.and　97.5％Sel.).This　work　provides　a　feasible　method　for　designing　COFs　with　high　photocatalytic　activity　by　adjusting　exciton　binding　energy.