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　photocatalytic　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.　(c)　2023　Published　by　Elsevier　B.V.　on　behalf　of　Chinese　Chemical　Society　and　Institute　of　Materia　Medica,　Chinese　Academy　of　Medical　Sciences.