The development of efficient, metal-free photocatalysts for solar-driven CO2 reduction to methanol is promising for alleviating energy and environmental issues, but achieving high selectivity and conversion efficiency without sacrificial agents or co-catalysts remains a challenge. In this work, we report a series of acetylene-linked specialized donor–acceptor (D–A) type conjugated microporous polymers (CMPs) designed with tailored electronic structures to investigate their efficacy in photocatalytic CO2 reduction to methanol in an aqueous NaOH solution under visible light irradiation. Significantly, the optimized porous polymer TTT-DEBP, featuring a strong electron-accepting triazine ring and an extended π-conjugated diethynyl biphenyl (DEBP) system, achieved a higher CH3OH production rate of 30.8 µmol g−1h−1 with 90.3% selectivity and excellent recyclability. Experimental and theoretical investigations revealed that the synergistic effect of triazine, biphenyl, and acetylene moieties of the porous network reduces exciton binding energy, enhancing charge separation and transfer, and reduces charge recombination for improved photocatalytic performance.