Herein, based on the strategy of synergetic catalysis, we report a cobalt-based coordination polymer PEI₆-Co. As a heterogeneous catalyst, PEI₆-Co shows a selectivity of 95% and a yield of 1170 mmol g⁻¹ for visible-light-driven CO₂-to-CO conversion in a water containing system, which is almost 2.8 times that of the mononuclear cobalt catalyst CoL¹ and is comparable to that of the dinuclear cobalt catalyst Co₂L.