Photocatalytic　water　splitting　is　an　ideal　pathway　to　produce　hydrogen　for　the　future　energy　supply　due　to　the　sustainability　of　solar　energy　and　the　mild　reaction　conditions.　In　the　past　four　decades,　many　inorganic　semiconductor　photocatalysts　have　been　studied　for　this　purpose.　In　recent　years,　conjugated　polymers,　in　particular　covalent　carbon　nitride　frameworks,　have　rapidly　emerged　as　a　new　family　of　photocatalysts.　However,　the　use　of　conjugated　photocatalysts　in　overall　water　splitting　in　the　absence　of　sacrificial　agents　has　been　much　less　reported.　Herein,　we　used　surface　kinetic　control　to　photocatalyze　overall　water　splitting　by　a　covalent　carbon　nitride　semiconductor　with　a　crystalline　poly(triazine　imide)　(PTI)　frameworks.　Our　study　demonstrates　that　the　loading　of　a　Pt　co-catalyst　on　the　PTI　surface　plays　the　key　role　in　inducing　overall　water　splitting.　The　co-deposition　of　a　cobalt　species　can　effectively　increase　the　photocatalytic　activity　and　adjust　the　ratio　of　H2　and　O2　produced,　as　well　as　enhancing　the　stability　of　the　photocatalyst.　The　optimal　sample　with　the　dual　co-catalysts　shows　an　apparent　quantum　yield　of　2.1%　for　the　overall　water　splitting　reaction.　©　2017　The　Royal　Society　of　Chemistry.