Graphitic　carbon　nitride　(g-CN)　is　an　emerging　metal-free　photocatalyst　for　solar　energy　conversion　via　water　splitting　and　CO2　fixation.　Herein,　we　used　preheated　melamine　as　a　starting　material　in　combination　with　the　salt　melt　method　to　synthesize　a　crystalline　tri-s-triazine-based　g-CN.　The　as-obtained　sample　exhibited　high　stability　and　photocatalytic　activity　toward　hydrogen　and　oxygen　production　from　water　splitting.　In　addition,　by　adding　phosphate　to　mimic　natural　photosynthetic　environment,　the　apparent　quantum　yield　(AQY)　for　the　hydrogen　production　reached　50.7%　at　405　nm,　which　is　the　highest　value　ever　reported　for　conjugated　carbon　nitride　polymers　in　hydrogen　evolution　photocatalysis.　The　results　of　this　study　demonstrate　that　crystalline　covalent　tri-s-triazine　frameworks　hold　great　promise　for　solar　energy　applications.　©　2016　American　Chemical　Society.