Cyclic carbonates as industrial commodities offer a viable non-redox carbon dioxide fixation, and suitable heterogeneous catalysts are vital for their widespread implementation. Here we report a highly efficient heterogeneous catalyst for CO2 addition to epoxides based on a newly identified active catalytic pocket consisting of pyridine, imine and phenol moieties. The polymeric, metal-free catalyst derived from this active site converts less reactive styrene oxide under atmospheric pressure in quantitative yield and selectivity to the corresponding carbonate. The catalyst doesn’t need additives, solvents, metals or co-catalysts, can be reused at least 10 cycles without loss of activity, and scaled up easily to a kg scale. DFT calculations reveal that the nucleophilicity of pyridine base gets stronger due to the conjugated imines and H-bonding from phenol accelerates the reaction forward by stabilizing the intermediate.