Supramolecular organic framework for recyclable heterogeneous photocatalysis of the reductive dechlorination of α-Chloroacetophenones and acetylation of amines with thioacetate

Abstract

Due to the urgent demand for environmentally friendly synthetic methods, metal-free materials have gained increasing prominence in various photocatalytic organic transformations. The utilization of supramolecular organic frameworks (SOFs) as photocatalysts has gradually emerged in photo-induced organic reactions, which complements the widespread use of porous organic polymers and covalent organic frameworks. SOFs, which are constructed through noncovalent interactions, can function as heterogeneous catalysts due to their low solubility in typical organic solvents. The present study reports the application of a SOF for heterogeneous photocatalysis. A tetraphenylmethane-based monomer (TM) incorporating four 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(1-methyl-1-pyridinium) units (MPT) has been synthesized and co-assemble with cucurbit[8]uril (CB[8]) to afford a photoactive three-dimensional supramolecular organic framework (TM-SOF) through the encapsulation of two MPT units by CB[8]. Various methods have been employed to characterize the optical and electronic properties of TM-SOF and reveal its exceptional light-absorbing properties that facilitate photoredox catalysis by generating reactive radical species. As a heterogeneous photocatalyst, TM-SOF efficiently catalyzes photoinduced reductive dichlorination of α-chloroacetophenones and acetylation of amines with thioacetate with high recyclability. Mechanistic studies were further conducted to reveal the effect of the framework on the photocatalytic efficiency of the MPT unit.