Photocatalytic　CO2　reduction　offers　a　promising　strategy　to　mitigate　the　greenhouse　effect,　yet　it　remains　a　challenging　process　due　to　the　high　energy　barrier　associated　with　the　high　stability　of　CO2.　In　this　study,　we　synthesized　Py-bTDC,　a　pyrene-based　covalent　organic　framework　(COF)　enriched　with　nitrogen　and　sulfur　atoms,　and　anchored　palladium　nanoclusters　(Pd　NCs)　onto　its　structure　to　enhance　CO2　reduction　efficiency.　The　confined　Pd　NCs　amplify　the　built-in　electric　field　(IEF),　enabling　efficient　photogenerated　carrier　migration　and　suppressing　electron-hole　recombination.　Simultaneously,　Pd　NCs　serve　as　catalytic　active　sites,　optimizing　CO2　adsorption　and　activation.　Density　functional　theory　(DFT)　calculations　reveal　that　Pd　reduces　the　energy　barrier　for　forming　the　critical　intermediate　(*COOH),　thereby　accelerating　CO　production.　Under　visible-light　irradiation　in　a　gas-solid　system　using　water　as　a　proton　donor,　the　Pd-3/Py-bTDC　composite　achieved　a　CO　evolution　rate　of　17.75　mu　molh(-1)g(-1)　with　86.0%　selectivity.　This　study　advances　the　design　of　COF-based　photocatalysts　by　synergistically　modulating　IEF　and　the　engineering　active　sites　for　efficient　CO2　reduction.