Carbon capture and sequestration (CCS) has been proposed to reduce CO2 emissions from large stationary sites such as coal-fired power plants. Currently, however, implementing CCS in power plants is not economically feasible due to the high expense of removing CO2 from flue gas. There is therefore an urgent need for cost effective CO2 capture technologies, such as efficient solid adsorbents. In this study, we develop a facile strategy that converts a cost-effective porous organic polymer (denoted as PP), which is synthesized by Friedel-Crafts alkylation reaction of dichloro-p-xylene, into outstanding CO2 adsorbents through one-step post-synthesis functionalization with polyamines. Among the adsorbents synthesized, PP-2-DETA and PP-2-TEPA show superior high CO2 uptake capacities, excellent CO2 selectivity over N-2, and appropriate Q(st). Furthermore, the adsorbents show good CO2 uptake capacity and excellent stability toward both water vapor and regeneration cycles under dynamic flow conditions. Significantly, our samples exhibite much faster adsorption-desorption kinetics than mmen-Mg-2 (dobpdc) and MCM-41-NH2, which are two outstanding amine-functionalized adsorbents.