A series of p-substituted pyridinium catalysts were investigated as sustainable organic catalysts for carbon dioxide utilization under ambient conditions. Dimethylaminopyridine hydroiodide (DMAP·HI) was found to be a superior catalyst for cyclic carbonate synthesis from epoxide and CO2 without solvents or additives. Mechanistic studies indicated that DMAP played a pivotal role as a nucleophile toward carbon dioxide during the cyclic carbonate formation. The organic catalyst could be recycled without any significant loss of catalytic activity, and was successfully applied for the multigram-scale synthesis of cyclic carbonate at mild temperature under atmospheric carbon dioxide.