Synthesis of hierarchically mesoporous polymeric carbon nitride with mesoporous melamine as a precursor for enhanced photocatalytic performance

Constructing mesoporous structure in polymeric carbon nitride (CN) is an effective way to enhance the photocatalytic performance, but rare work achieved this through controlling morphologies of raw materials because of their easy fusion on calcination. Herein, mesoporous melamine (MMA) comprising nanorods was prepared via facile acid processing on commercial MA (CMA), with ~40 times increased specific surface area. By jointly using MMA and the gas template (NH 4 Br) as the precursor for the first time, hierarchically mesoporous CN (HMCN) was simply synthesized with much thinner nanosheets, ~4 times higher specific surface area, stronger photoabsorption, and faster charge separation than bulky CN. On this account, HMCN exhibits much higher photoactivity in H 2 production and for environmental purification. Its visible-light photocatalytic H 2 evolution rate, 1412 μmol g –1  h −1 is ~8.9 times that of bulky CN, and reactive oxygen species generation rates are prominently higher than those of CN. The chemical stability of HMCN in the photoreactions is satisfactory. This work provides a simple way to prepare MMA and a novel strategy to synthesize HMCN, which may guide synthesis of other mesoporous CN-based photocatalysts.