It　is　a　challenge　to　explore　photocatalytic　materials　for　sunlight-driven　water　splitting　owing　to　the　limited　choice　of　a　single　semiconductor　with　suitable　band　energy　levels　but　with　a　minimized　band　gap　for　light　harvesting.　Here,　we　report　a　one-photon　excitation　pathway　by　coupling　polymeric　carbon　nitride　(PCN)　semiconductor　with　LaOCl　to　achieve　overall　water　splitting.　This　artificial　photosynthesis　composite　catalyzes　the　decomposition　of　H2O　into　H(2)and　O-2,　with　evolution　rates　of　22.3　and　10.7　mu　mol　h(-1),　respectively.　The　high　photocatalytic　performance　of　PCN/LaOCl　can　be　ascribed　to　the　simultaneously　accomplished　reduction　and　oxidation　of　water　on　LaOCl　and　PCN　domains,　respectively,　as　well　as　the　fast　charge　separation　and　migration　induced　by　the　interfacial　electric　field　related　to　LaOCl　modification.　This　study　provides　new　insights　on　the　development　of　composite　photocatalysts　for　pure　water　splitting　based　on　polymer-based　materials　via　charge　modulation.