Cosolvent-free nanocasting synthesis of ordered mesoporous g-C3N4 and its remarkable photocatalytic activity for methyl orange degradation

Abstract

Ordered mesoporous g-C₃N₄ (ompg-C₃N₄) was synthesized in an aqueous solution via a green cosolvent-free nanocasting route by replacing the extremely virulent cyanamide with the environment-friendly starting material dicyandiamide (DCDA) for the first time. The well-defined cashew-shaped ompg-C₃N₄ was obtained when the weight ratio of DCDA to mesoporous silica SBA-15 was controlled at 2 : 1 in the nanocasting process. The excellent photocatalytic performance towards the degradation of methyl orange (MO), a hazardous dye, was evaluated under visible light irradiation and the degradation rate constant of ompg-C₃N₄ was determined to be 30 times as high as that of bulk g-C₃N₄. The significantly enhanced photodegradation activity of ompg-C₃N₄ is mainly attributed to the ordered mesopores inside individual particles, which accelerate the adsorption of the dye onto the catalyst surface and shorten the diffusion path of free carriers from the bulk phase to the surface, thereby enhancing the separation efficiency of photogenerated electrons and holes. In addition, a possible MO photodegradation mechanism was proposed based on the results of the control experiments in the presence and absence of scavengers.