A benzothiadiazole-vinyl-linked POSS porous hybrid polymer enables photocatalytic oxidative coupling of amines in air

Abstract

Rational design of metal-free porous photocatalysts is essential for advancing sustainable visible-light-driven organic transformations. Herein, we report the facile synthesis of novel benzothiadiazole-functionalized vinyl-POSS porous hybrid polymers (denoted as BTV-PHPs) via a one-step Heck coupling reaction between octavinylsilsesquioxane (VPOSS) and 4,7-dibromo-2,1,3-benzothiadiazole (DB-BT) at different molar ratios. The optimal polymer BTV-PHP-4 features a well-defined donor–acceptor (D–A) architecture, with vinyl-functionalized POSS serving as the electron donor and benzothiadiazole as the electron acceptor. This unique structure endows the polymer BTV-PHP-4 with pronounced radical character, broad visible-light absorption, and efficient photoinduced charge separation. Furthermore, BTV-PHP-4 exhibits excellent thermal stability, a hierarchical micro/mesoporous structure (BET surface area: 405 m² g⁻¹), and a fluffy nanoarchitecture. As a metal-free heterogeneous photocatalyst, BTV-PHP-4 achieves nearly quantitative conversion (99%) and high selectivity (99%) in the solvent-free photocatalytic oxidative coupling of benzylamine to N-benzylidenebenzylamine under blue LED irradiation in ambient air, while simultaneously generating H₂O₂ and NH₃ as valuable co-products. Mechanistic investigations indicate that both superoxide radical anions (O₂˙⁻) and singlet oxygen (¹O₂), generated via photoinduced electron transfer and energy transfer, respectively, serve as crucial reactive oxygen species in the photocatalytic process. This work provides a universal strategy for constructing vinyl-POSS-derived porous polymers with tailored photoactive units for sustainable photocatalytic applications.