The nitrogen-containing hierarchical porous polymers (NHPPs), which possessed micropores, mesopores, and marcopores simultaneously, were constructed by introducing micropores and mesopores into polystyrene foam by post cross-linking of the skeleton via Friedel Crafts reaction. First, polystyrene foams with abundant macropores (voids and windows) were obtained by concentrated emulsion polymerization. Subsequently, micropores and mesopores were generated by post-cross-linking cyanuric chloride into the skeleton of polystyrene foam. Cyanuric chloride was used as external cross-linker because of its rich nitrogen content. Finally, NHPPs with high specific surface areas (up to 1226 m(2)/g) were obtained. The effects of volume fraction of the dispersed phase of concentrated emulsion, DVB in polystyrene matrix, external cross-linker, and solvent on the textural properties of NHPPs were investigated. Then NHPPs were applied as CO2 absorbent, and the maximum CO2 capacity of 141 mg/g at 273 K, 1 bar and the good reproducibility were achieved. Furthermore, the tentative adsorption mechanism of triazine-ring in NHPPs to CO2 was proposed. Most importantly, the relationship between the structures of NHPPs and their CO2 adsorption capacities was analyzed. The results indicated that the CO2 capacities mostly depended on the microporous volume, and the nitrogen content also had impact on the CO2 capacities.