Because of their high stability, abundant porosity, and tailorable surface properties, N-doped porous carbons (NPCs) have played a crucial part in CO2 capture. Development of an efficient and low-cost method to fabricate NPCs remains a significant challenge. Herein, we report for the first time the preparation of NPCs through the rational design of the N-enriched polymer NUT-20-EDA (NUT, Nanjing Tech University; EDA, ethylenediamine) as the precursor. The NUT-20-EDA was obtained by polymerization of two simple monomers of mesitylene and formaldehyde dimethyl acetal, followed by post-synthetic ammonification. Through carbonization at temperatures ranging from 600 degrees C to 800 degrees C, NPCs with different porosity and N contents are fabricated, successfully. The reference porous carbons (rPCs) are also synthesized based on the polymer NUT-20 without post-synthetic ammonification. For the representative sample generated at 700 degrees C (NPC-700), the surface area is up to 1852 m(2)/g, which is much larger than its counterpart rPC-700 (1324 m(2)/g). Moreover, the CO2 uptake of NPC700 (7.1 mmol/g at 0 degrees C and 1 bar) is higher than that of rPC-700 (5.9 mmol/g), and also superior to those of many benchmarks reported, including 13X zeolite (4.1 mmol/g) and activated carbon (2.8 mmol/g). Therefore, it is proved that, as a pore-foaming agent during the carbonization, the amino groups incorporated play a significant role in the formation of abundant porosity of the NPCs, which is one of the crucial factors for CO2 adsorption, and the N-species doped in NPCs can work as the CO2-philic sites to enhance the CO2 capture.