Red-light-driven oxidation of aryl thioethers via a superoxide radical-generating zinc(II) metal-organic chain photocatalyst.

The development of sustainable and red-light-responsive photocatalytic systems for selective oxidation of aryl thioethers is a pressing challenge in the field of eco-friendly organic synthesis. Herein, we report the rational design and fabrication of a novel one-dimensional (1D) zinc(II) metal organic chain (MOC-1) by integrating 5,10-dihydrophenazine-based red-light-harvesting ligands with zinc(II)-hydroxide clusters. MOC-1 exhibits strong absorption in the red-light region (600-800 nm), efficient charge carrier separation, and the capability of in situ generating superoxide radicals (O2˙-) under red-light irradiation. Structural characterization confirms that MOC-1 is a crystalline 1D Zn(II)-organic coordination chain, in which the individual chains further assemble into a higher-dimensional supramolecular architecture. Mechanistic studies indicate that the 5,10-dihydrophenazine-based ligand enables red-light harvesting, while the coordination-induced electronic structure of MOC-1 facilitates photoinduced charge transfer and the reduction of molecular oxygen to superoxide radicals. Under red-light irradiation (660 nm), MOC-1 exhibits excellent catalytic activity and selectivity in the aerobic oxidation of various aryl thioethers, affording the corresponding sulfoxides with yields up to 98% and negligible overoxidation to sulfones. The mesoporous framework of MOC-1 not only provides abundant accessible active sites but also stabilizes the key aryl thioethers radical cation intermediates, ensuring high reaction selectivity. Furthermore, its robust chemical stability and resistance to photodegradation enable five consecutive recycling cycles with no significant loss of catalytic activity. This work establishes a new paradigm for red-light-driven, noble-metal-free photocatalysis by leveraging organic polymer-confined dual-functional sites (light-harvesting ligands and redox-active metal centers), thereby advancing the development of sustainable and energy-efficient synthetic protocols for thioether oxidation.