Red-Light-Driven C(sp2)–H Sulfonylation of Anilines Using a Recyclable Benzothiadiazole-Based Covalent Organic Framework

The limitations of traditional high-energy (NUV or blue) photocatalysis, such as limited penetration in reaction media, off-target reactivity, and health hazards, have spurred the development of seminal red-light-mediated transformations. Despite recent advances, most homogeneous red-light photocatalysts suffer from poor recyclability, and recyclable heterogeneous systems remain underexplored. Herein, we report a red-light-driven C(sp2)–H sulfonylation of anilines using a highly stable benzothiadiazole-based covalent organic framework (Tp-BT COF) as an efficient, recyclable photocatalyst. The reaction proceeds under exceptionally mild conditions, affording sulfonylated products in good to excellent yields with minimal catalyst loading. Notably, the Tp-BT COF retains its catalytic activity over six consecutive cycles. Comparative studies with structurally related COFs highlight the critical role of the BT core in red-light absorption and the superior performance of the AA stacking mode. This work underscores the potential of rationally designed photoactive COFs for sustainable red-light photocatalysis.