Self-assembled synthesis of benzene-ring-grafted g-C3N4 nanotubes for enhanced photocatalytic H2 evolution

An innovative benzene-ring grafted g-C3N4 nanotubes (AHCN) were prepared by thermal-polymerization of the self-assembled supramolecular composed of melamine (MA) and phloroglucinol (PG). MA is molecular self-assembly with PG to form nanorod-like supramolecular intermediate (N-MA-PG) in the hydrothermal process. Consequently, the PG in N-MA-PG acts as in-situ benzene-ring-doping source and shape-preserving-agent in the thermal polymerization conversion of N-MA-PG to AHCN. Benefited from the synergistic effect of nanotubular structure and benzene-ring grafting, AHCN shows stronger visible-light absorption, higher surface area, enhanced charge's separation efficiency, leading to an excellent photocatalytic H-2 evolution rate of 2780 mu mol h(-1) g(-1) under visible light irradiation, which is obviously superior to that of pristine g-C3N4 (187 mu mol h(-1) g(-1)), g-C3N4 nanotubes (512 mu mol h(-1) g(-1)) and benzene-ring grafted g-C3N4 (666 mu mol h(-1) g(-1)). The apparent quantum efficiency of AHCN is achieved at 6.21 % at lambda = 420 nm. This work proposes a route to develop high-photocatalytic activity g-C3N4 through nanostructure controlling and molecular doping simultaneously.