Aqueous ionic self-assembly of a donor–acceptor viologen and eosin Y-based porous ionic salt for enhanced photocatalytic aerobic oxidation

Abstract

Rational design of metal-free heterogeneous photocatalysts via facile synthesis is critical for advancing green sustainable visible-light-driven organic transformations. Herein, we construct a photoactive viologen and eosin Y-based porous ionic salt (VEY-PIS) with electron donor–acceptor (D–A) structures by room-temperature aqueous ionic self-assembly of low-cost aminoethyl-functionalized viologen cations (VIL-AM, electron acceptor) and dye eosin Y anions (EY-2Na, electron donor). The ingenious combination of viologen and eosin Y ion pairs endows the porous VEY-PIS framework with significant radical character, broad visible-light absorption, and highly efficient photoinduced charge transfer capability. Leveraging these synergies, the heterogeneous photocatalyst VEY-PIS achieves exceptional activity in both the aerobic photocatalytic oxidative coupling of benzylamines and oxidation of sulfides under ambient air. Mechanistic studies reveal efficient electron transfer between D–A ion pairs—viologen cations and eosin Y anions—boosting photocatalytic oxidation. This work establishes a general, facile ionic self-assembly approach to design task-specific D–A structured porous ionic salts by pairing tailored viologen cations with various anionic dyes, offering a new kind of heterogeneous photocatalyst for photocatalytic organic reactions.