Photocatalytic hydrogen production from water is a promising strategy for the direct conversion of sunlight into chemical energy, which is considered as a long-term and sustainable solution to address worldwide energy and environmental issues. Herein, we develop carbon doped boron nitride (BCN) as metal-free photocatalysts by using solid-gas reaction and molecular design method of boron source. Four kinds of boron carbon nitride (BCN) were synthesized through mixed glucoses with melamine phosphate borate (MPB), melamine borate (MB), boric acid (BA) and boron oxide (BO), respectively. It can be found that the morphology of BCN-MPB (nanosheets) is different from bulk BCN-MB, bulk BCN-BA and bulk BCN-BO. The BCN-MPB nanosheets show much higher specific surface area, the longer lifetime of photoexcited charge carriers, and the stronger electron transport ability compared to those of bulk BCN. Thus, BCN-MPB nanosheets exhibit significantly improved photocatalytic hydrogen activities under visible light illumination compared to those of bulk BCN. Our work represents a facile and template-free synthesis strategy for the rational design of eco-friendly, stable and inexpensive photocatalysts, and paves new pathways for tuning their photoreactivity in sustainable light-to-energy conversion.