In this report, porous carbons were made via a facile single-step KOH activation of commercial phenolic resin. Different from the conventional carbonization-activation two-step procedure, this work combines the carbonization and activation into one step to achieve carbons with a well-developed porous structure. The as-attained carbonaceous adsorbents possess good CO2 uptake under atmospheric pressure, 4.12 and 6.02 mmol/g at 25 and 0 degrees C, respectively. Detailed research pointed out that the synergetic effects of volume of narrow micropores, pore size, and pore size distribution of the adsorbents determine the CO2 uptake under 1 bar and 25 degrees C for these phenolic resin-derived adsorbents. In addition to the excellent CO2 adsorption capacities, these sorbents also have other exceptional CO2 adsorption properties like high CO2/N-2 selectivity, intermediate heat of adsorption, quick adsorption kinetics, excellent recyclability, and high dynamic adsorption capacity. These features suggest that the porous carbons prepared by the facile single-step strategy are promising for CO2 removal from industrial gas streams.