Bifunctional Covalent Organic Frameworks Enable Ambient Photocatalytic Oxidation via Synergistic Ligand-to-Metal Charge Transfer and O₂Activation

Covalent organic frameworks (COFs) offer a powerful platform for photocatalysis, yet integrating multiple catalytic functions within a single structure remains challenging. Here, we report the synthesis of dual-functionalized COFs, FeP-Me(AA) and FeP-Me(AB), integrating photosensitizing iron–porphyrin motifs and redox-active iminium linkages, with AA and AB stacking modes controllable through distinct synthetic procedures. Under light irradiation, the COFs efficiently catalyze C–H and alcohol oxidations directly under air at room temperature, without requiring sacrificial reagents. FeP-Me(AA) exhibits superior activity compared to nonmethylated and nonmetalated COF analogues as well as homogeneous catalysts, underscoring the advantages of dual-site integration. Mechanistic studies reveal a bifunctional pathway: the iron–porphyrin units undergo ligand-to-metal charge transfer to generate reactive chlorine or hydroxyl radicals that mediate hydrogen atom transfer to generate carbon-centered radicals, while adjacent iminium linkages transfer electrons to reduce O₂ to superoxide radicals. Coordination of these radicals to Fe(III)(TPP) forms an iron(III)–peroxide intermediate, which undergoes subsequent O–O bond cleavage to generate the ketone product. By uniting cooperative functions within a single framework, this work establishes a versatile blueprint for designing sustainable and synergistic photocatalysis with COFs.