Fluorenone Acceptor-Linker Engineering of Lead Halide MOFs for Aerobic Photocatalytic Oxidative Coupling

Lead halide hybrids possess attractive light-harvesting and charge-transport properties for photocatalytic organic synthesis, but their soft ionic lattices are vulnerable to polar liquid media. Coordination-stabilized lead halide frameworks improve chemical robustness, but conventional terephthalate linkers provide limited π-electronic interaction with lead-halide components, resulting in pronounced charge localization and inefficient carrier separation. Herein, we report a fluorenone acceptor-linker strategy to construct an electronically integrated lead halide-based metal-organic framework (MOF), Pb2Na2Cl2(fodc)2 (TMOF-24; fodc = fluorenone-2,7-dicarboxylate), based on one-dimensional [Pb2Cl2]2+ chains bridged by fluorenone-functionalized dicarboxylate linkers. An isoreticular noncarbonyl analogue, Pb2K2Cl2(fedc)2 (TMOF-23; fedc = fluorene-2,7-dicarboxylate), was synthesized as a control to clarify the role of the fluorenone acceptor. Compared with TMOF-23, TMOF-24 exhibits a substantially red-shifted absorption edge from 450 to 535 nm, a reduced exciton binding energy, weakened electron-phonon coupling, and a prolonged carrier lifetime. These features enable efficient visible-light-driven generation of superoxide radicals and singlet oxygen. As a result, TMOF-24 achieves fast, selective, and recyclable aerobic oxidative coupling of benzylamine with quantitative yield within 2 h, and maintains >95% yield over ten cycles. This work demonstrates that acceptor-linker engineering endows structurally robust lead halide MOFs with excellent charge-transfer characteristics for selective aerobic organic synthesis.