Capturing CO2 from large stationary sources, such as coal-burning power plants, has been proposed to limit the rise of average global temperature. Currently, however, it is not economically feasible to implement CO2 capture facilities in power plants due to their high energy consumption. In this regard, the development of efficient and cost-effective CO2 adsorbents is still an urgent requirement. We report a series of novel amine-containing solid materials prepared by synthesizing porous organic copolymers, labeled PBTP-(x), by copolymerization of 1,3,5-trichlorobenzyl and 4,4'-bis(chloromethyl) biphenyl, and sub sequently decorating the PBTP-(x) with alkylamines via a one-step postsynthetic grafting. Among the samples synthesized, PBTP-(1:4)-DETA displays a promising combination of high CO2 adsorption capacity, large CO2 selectivity over N-2, and fast sorption kinetics. Furthermore, it not only retains a high CO2/N-2, separation performance but also has outstanding stability under repeated adsorption-desorption cycling in the presence of water vapor under dynamic flow conditions, implying its potential application to postcombustion CO2 capture.