The　conjugated　co-monomer,　trimesic　acid　(TMA)　was　integrated　into　the　triazine　framework　of　polymeric　carbon　nitride　(PCN),　synthesized　through　chemical　condensation　of　urea.　The　TMA-modified　carbon　nitride　samples　obtained　were　named　as　CNU-TMA　and　it　was　utilized　for　the　photocatalytic　reduction　of　carbon　dioxide　(CO2)　under　visible　light　illumination.　The　induction　of　such　electron　donor-acceptor　co-monomer　(TMA)　dominates　the　intramolecular　structure　of　PCN　by　acting　as　a　nudeophilic　substitution　substrate　to　facilitate　the　electron　density　in　the　pi-electron　conjugated　system　of　PCN　and　thus　elevate　its　photocatalytic　activity.　Also,　this　process　of　copolymerization　with　TMA,　not　only　cause　a　significant　diversion　in　the　specific　area,　band　gap,　chemical　composition,　and　structure　of　PCN　but　also　promote　efficient　charge　transport　from　ground　state　(HOMO)　to　the　excited　state　(LUMO)　of　the　PCN.　For　comparison,　CNU　samples　modified　with　other　co-monomers　were　prepared　by　the　same　method　and　were　named　as　CNU-FDA　(2,5-Furandicarboxylic　acid),　CNU-PDA　(2,6-pyridinedicarboxylic　acid),　CNU-PTA　(Phthalic　acid).　Similarly,　co-monomer　TMA　was　incorporated　in　other　PCN　precursors　such　as　dyandicyanamide　(DCDA),　thiourea　(SCN)　and　ammonium　thiocyanate　(NH2SCN)　and　was　named　as　CND-TMA(13.0),　CNT-TMA(13.0),　and　CNA-TMA(13.0),　respectively.　Besides,　the　average　weight　ratio　between　urea　and　TMA　was　well　tuned　and　also　CNU-TMA(13.0)　gain　a　fabulous　16　fold-enhanced　photocatalytic　performance　than　blank　CNU.　(C)　2019　Elsevier　Inc.　All　rights　reserved.