The　structural　alteration　of　carbon　nitride　(CN)　for　photocatalytic　CO2　reduction　is　a　promising　research　topic　in　the　environmental　and　energy　sectors.　This　work　discusses　the　fabrication　of　photocatalyst　through　a　heterojunction　architecture　obtained　from　the　molecular　engineering　of　electron-rich　organic　monomer　2,6-pyridinedicarboxylic　acid　(PDA)　with　CN　precursor　(CN/PDAx).　The　successful　integration　of　PDA　in　the　structure　of　CN　served　as　a　charge　inducting　entity　to　enhance　charge　separation　and　photocatalytic　CO2　reduction　under　visible　light　(λ　=　420　nm).　The　DFT　results　indicated　that　the　upshift　in　the　HOMO　level　of　CN　after　integration　of　PDA　in　its　framework　was　the　most　lawful　for　the　charge　separation　and　for　obtaining　a　high　reduction　potential.　As-synthesized　photocatalysts　were　demonstrated　for　various　integral　analysises　and　after　evaluating　the　process　of　photocatalytic　CO2　reduction　under　visible　light　region　(λ　=　420　nm).　The　optimized　sample　CN/PDA10　has　the　most　excellent　photocatalytic　activity　producing　85.4　μmol/h　of　CO　and　21.3　μmol/h　of　H2,　achieving　a　7.5-fold　enhanced　catalytic　efficiency　as　compared　to　pure　CN.　We　hope　that　this　work　will　attract　more　attention　to　synthesizing　efficient　photocatalysts　for　energy　production　and　environmental　remediation.　©　2022　Vietnam　National　University,　Hanoi