N-enriched porous carbons have played an important part in CO₂ adsorption application thanks to their abundant porosity, high stability and tailorable surface properties while still suffering from a non-efficient and high-cost synthesis method. Herein, a series of N-doped porous carbons were prepared by a facile one-pot KOH activating strategy from commercial urea formaldehyde resin (UF). The textural properties and nitrogen content of the N-doped carbons were carefully controlled by the activating temperature and KOH/UF mass ratios. As-prepared N-doped carbons show 3D block-shaped morphology, the BET surface area of up to 980 m²/g together with a pore volume of 0.52 cm³/g and N content of 23.51 wt%. The optimal adsorbent (UFK-600-0.2) presents a high CO₂ uptake capacity of 4.03 mmol/g at 0 °C and 1 bar. Moreover, as-prepared N-doped carbon adsorbents show moderate isosteric heat of adsorption (43–53 kJ/mol), acceptable ideal adsorption solution theory (IAST) selectivity of 35 and outstanding recycling performance. It has been pointed out that while the CO₂ uptake was mostly dependent on the textural feature, the N content of carbon also plays a critical role to define the CO₂ adsorption performance. The present study delivers favorable N-doped carbon for CO₂ uptake and provides a promising strategy for the design and synthesis of the carbon adsorbents.