A facial, template-free and green strategy was developed to prepare C-doped hollow spherical g-C3N4 derived from supramolecular self-assembly of melamine, glucose and cyanuric acid. Especially, the precursors were tightly connected by hydrogen bonds, wherein glucose was served as a source of doped carbon. Spectroscopic and electrochemical analysis confirmed that the endmost nitrogen was replaced by the doped carbon to combine two melon parts, leading to the possible existence of the delocalized big pi bonds in the system. Moreover, the GCN-x not only maintained the excellent properties of the hollow sphere, such as high surface area, moderate porosity and short charges diffusion distance, but also overcame the drawbacks of low visible light response and high electron-holes recombination rate from bulk g-C3N4. Thereby, the visible light utilization rate and the photogenerated electron-holes separation efficiency of the catalyst were improved. The highest hydrogen yield of 305 mu mol h(-1) from GCN-0.2 was 28.5 times that of bulk g-C3N4. Finally, a possible mechanism underlying the photocatalytic performance of C-doped g-C3N4 hollow spheres was proposed tentatively. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.