Solar-driven　syngas　generation　by　CO2　reduction　provides　a　sustainable　strategy　to　produce　renewable　fossil　fuels.　Nevertheless,　this　promising　approach　often　suffers　from　tough　CO2　activation,　sluggish　reaction　kinetics　and　complex　selectivity.　Herein,　we　exquisitely　constructed　spatially　directional　charge　transport　channel　over　two-dimensional　transition　metal　chalcogenide　(TMC)-based　heterostructure　via　a　facile　and　universal　electrostatic　self-assembly　method.　Tailor-made　positively　charged　non-conjugated　insulating　polymer　of　poly(diallyl-dimethyl-ammonium　chloride)　(PDDA)　and　negatively　charged　graphene　oxide　(GO)　precursor　as　building　blocks　are　controllably　anchored　on　the　TMC　substrate,　by　which　ultrathin　PDDA　layer　is　intercalated　at　the　interface　of　GO　and　TMC.　We　ascertain　that,　in　this　customized　sandwiched　heterostructures,　PDDA　interim　layer　functions　as　an　electron-relaying　mediator,　whilst　graphene　(GR)　obtained　from　in-situ　GO　reduction　during　the　photocatalytic　reaction　serves　as　a　terminal　electron-trapping　reservoir,　synergistically　facilitating　the　spatially　vectorial　charge　separation/migration　over　TMC,　thus　endowing　the　TMC/PDDA/GR　heterostructures　with　conspicuously　enhanced　visible-light-driven　photoactivity　toward　CO2-to-syngas　conversion.　Our　work　would　inspire　judicious　ideas　for　finely　modulating　charge　transfer　over　polymer-mediated　photosystems　and　benefit　our　fundamental　understanding　of　solar　CO2　conversion.