A macroscopic 3D porous graphitic carbon nitride (g-CN) monolith is prepared by the one-step thermal polymerization of urea inside the framework of a commercial melamine sponge and exhibits improved photocatalytic water splitting performance for hydrogen evolution compared to g-CN powder due to 3D porous interconnected network, larger specific surface area, better visible light capture, and superior charge separation efficiency. 

Adv Mater. 2015