The rapid growth of CO2 emissions, especially from power plants, has led to the urgent need to directly capture and fix CO2 in the flue gas after simple purification rather than energy-intensive gas separation. Herein, imidazolium-functionalized ionic hypercrosslinked porous polymers (HCPs) bearing adjustable surface groups were straightforwardly synthesized through co-hypercrosslinking of benzylimidazole salts and crosslinker through Friedel-Crafts alkylation. Abundant microporosity and relatively high ionic moieties were obtainable in the ethyl-group-tethered ionic HCP, giving a remarkably selective CO2 capture performance with a CO2 uptake of 3.05 mmol g-1 and an ideal adsorbed solution theory (IAST) CO2 /N2 selectivity as high as 363 (273 K, 1 bar). This ionic polymer demonstrated high efficiency in the synthesis of cyclic carbonates from the coupling of various epoxides with the simulated flue gas (15 % CO2 and 85 % N2 ), giving high yields, large turnover numbers (up to 4800), and stable reusability under additive- and solvent-free conditions.