A　chemical　protocol　based　on　molecular　engineering　of　polymeric　matrix　is　developed　for　the　chemical　optimization　of　ordered　mesoporous　carbon　nitride　(OMCN)　in　this　study　to　address　the　concerns　on　the　serious　nanostructure-induced　semiconductive　defects,　in　particular　the　remarkable　hypsochromic　shift　of　absorption　threshold　and　the　increased　excition　dissociation　energy.　Physical　characterizations　demonstrate　that　the　successful　incorporation　of　3-aminothiophene-2-carbonitrile　(ATCN)　aromatic　donor　in　OMCN　matrix　can　efficiently　extend　the　pi-conjugated　system,　red-shift　the　optical　absorption　toward　longer　wavelengths　and　promote　exciton　splitting,　thus　well　overcoming　the　serious　semiconductive　defects.　In　addition,　the　unique　structural　benefits　of　OMCN,　such　as　the　well-orientated　nanoarchitectures　with　large　specific　surface　area　and　uniform　nanosized　pore,　have　been　well　remained　in　ATCN-modified　sample　(OMCNA)　via　adjusting　the　ATCN/cyanamide　molar　ratio　to　minimize　the　unavoidable　matrix　disturbance.　Hence,　an　obviously　enhanced　photocatalytic　activity　toward　H-2　evolution　and　selective　oxidation　of　alcohols　are　obtained　on　optimized　OMCNA　samples,　greatly　underlining　the　advantage　of　molecular　engineering　in　supporting　nanostructured　photocatalysts.　(C)　2016　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.　and　Science　Press.　All　rights　reserved.