In this study, we have prepared novel pyrrole-formaldehyde polymers through polymerizing pyrrole and formaldehyde in the mixture solvent of water and ethanol by using hydrochloric acid as a catalyst. The as-synthesized polymers possess a nitrogen content of 6.7 atom % and are composed of spherical particles with the diameter of approximately 1-3 mu m. A series of nitrogen-doped porous carbons with high specific surface areas (680-2340 m(2) g(-1)) were successfully obtained through the activation treatment of the polymer spheres. The porous properties and surface chemistry of the as-prepared porous carbons are tuned by choosing different activating agents and changing the activation temperature. The morphology, porous properties, and chemical composition of the obtained nitrogen-doped porous carbons are revealed by various characterization methods, such as scanning electron microscopy, nitrogen sorption measurement, and X-ray photoelectron spectroscopy. The as-prepared nitrogen-doped porous carbons as gas adsorbents display high carbon dioxide uptake capacities of 3.80-5.81 mmol g(-1) at 273 K and 1.0 bar. They also show excellent carbon dioxide adsorption capacities (2.40-3.37 mmol g(-1) at 1.0 bar) and good gas selectivities (CO2/N-2 selectivities of 16.9-70.2) at 298 K.