Bifunctional Covalent Organic Frameworks Enable Ambient Photocatalytic Oxidation via Synergistic Ligand-to-Metal...

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.