Highly crystalline multi-component covalent organic frameworks for photocatalytic organic conversion

Abstract

Covalent organic frameworks (COFs) have been considered as a family of attractive photocatalysts, which have shown unique advantages in photocatalytic applications. Multicomponent polycondensation strategy is growing as one of the most important methods for syntheses of functionalized COFs materials. Herein, under solvothermal conditions, four building blocks of 2‑hydroxy-1,3,5-benzenetrialdehyde (HTB), 2,4,6-trihydroxy-1,3,5-benzenetrialdehyde (TTB), benzidine (BD), 3,3′-dimethyl-[1,1′-biphenyl]-4,4′-diamine (DMBZ) were selected to synthesize ketoenamine-linked framework material DBTH4-COF with high crystallinity and stability. The resultant COF has a suitable optical band gap, strong photocurrent response and low impedance, indicative of high potential for heterogeneous photocatalysis. After evaluation, DBTH4-COF exhibited the preminent photocatalytic performance in photosynthesis of benzimidazoles. Cycling experiments also showed high stability and recyclability of the DBTH4-COF. The high-performance DBTH4-COF was further employed as a heterogeneous catalyst for photocatalytic oxidative of amines to imines and oxidation of tetrahydroisoquinoline to dihydroisoquinolone. Some control experiments were performed to gain further insights into the nature of photocatalysis. The current research also provided a valuable approach for developing COFs catalysts to meet challenges in photocatalytic organic transformations.