•Carbons were derived from modified phenol–formaldehyde resin via steam activation.•The surface area up to 1439m2g−1 was reached at an activation temperature of 950°C.•The N content of activated carbons decreased with increasing activation temperature.•A maximum CO2 adsorption capacity of 6.71molkg−1 was attained at 273K and 1atm.•The adsorption isotherms of CO2 could be described by the Redlich–Peterson equation. Highly porous activated carbons were prepared from melamine-modified phenol–formaldehyde resins via steam activation at different activation temperatures (700–950°C) and then used for CO2 capture at atmospheric pressure. The porosity and surface properties of the activated carbons and their CO2 adsorption capabilities were studied and compared with those derived from common phenol–formaldehyde resin. An adsorption capacity for CO2 of 6.71molkg−1 (29.5wt.%) was attained at 0°C and 1atm and decreased significantly with increasing operating temperature. The prepared activated carbons could be well applied in temperature-swing adsorption processes. Of the three isotherm equations (Langmuir, Freundlich, and Redlich–Peterson), the adsorption of CO2 on activated carbons could only be satisfactorily described using the three-parameter Redlich–Peterson equation.