Photochromic Bi 2 WO 6 /BiOBr ultrathin nanosheet heterojunctions for efficient photocatalytic synthesis of imine via toluene and aniline coupling

Abstract

Photocatalytic activation of inert C-H bonds followed by cross-coupling reactions driven by semiconductors represents an important organic synthesis strategy. However, photocatalytic synthesis of imines via toluene and aniline coupling over semiconductor photocatalysts remains a significant challenge owing to the high C-H bond dissociation energy of toluene and poor charge separation and transfer efficiency of photocatalysts. Herein, we report Bi 2 WO 6 /BiOBr ultrathin nanosheet heterojunctions (UNHs) with photochromic behaviors for photocatalytic oxidation of toluene followed by coupling with aniline to synthesis imines. The heterojunctions achieve 99% yield of imine, which is 7 and 5 times higher than that of pure Bi 2 WO 6 (14%) and BiOBr (20%) nanosheets, respectively. The Bi 2 WO 6 /BiOBr UNHs exhibit outstanding photocatalytic performance, owing to the synergistic effect of photochromism-induced W 6+ /W 5+ species and heterojunction engineering that expedites the separation and transfer of photogenerated charges, provides active sites for O 2 adsorption and activation to form superoxide radicals (O 2 •-), promotes the photooxidation of toluene to benzaldehyde and then cross-coupling with aniline to produce imines under 405 nm light irradiation. This present investigation offers a promising approach to the development of high-performance photocatalysts via combining photochromism and heterojunction engineering.