Thermal oxidative etching method derived graphitic C3N4: highly efficient metal-free catalyst in the selective epoxidation of styrene

Abstract

A series of g-C₃N₄ nanosheets were synthesized by thermal oxidation with long time heating and etching. With an increase in heating time from 1.0 to 3.0 h, the g-C₃N₄ nanosheet was obtained with a thinner layer thickness, larger BET surface area and higher graphic nitrogen ratio. As a metal-free heterogeneous catalyst, the g-C₃N₄ NS-3 h nanosheets show a superior catalytic performance for the epoxidation of styrene to styrene oxide than that of the bulk g-C₃N₄ and other recently reported metal-free materials. The higher activity of the g-C₃N₄ NS-3 h synthesized by long time thermal oxidative etching might be ascribed to the enlarged specific surface, pore volume and higher graphic nitrogen ratio with the loose and soft laminar morphology. The graphitic nitrogen species play a key role in the catalytic reaction based on a good linear correlation between the content of these species and the activity results. The g-C₃N₄ nanosheets are very stable and can be reused 5 times without obvious loss of catalytic activity.