The separation of CO2 from the nature gas is a challenge for solid sorbents. Bio-tar, a low cost and renewable carbon source, is employed to synthesis the ultra-microporous carbon materials. Carbonization of bio-tar with potassium hydroxide (KOH) at high temperatures (>700 degrees C) yields porous carbon materials with high surface areas of up to 2595 m(2) g(-1) and high CO2 uptake performance of 5.35 mmol g(-1) at 1 bar and 0 degrees C. This carbon material also shows good CO2/CH4 selectivity in mixed gas and excellent cyclability. In gas breakthrough test, the retention time of bio-tar-derived carbon for carbon dioxide and methane adsorption is 849 s g(-1) and 337 s g(-1), respectively. The retention time of CO2 is 157 s g-1 at 150 degrees C while CH4 is nearly non-adsorption. The carbon material has good cycle performance for carbon dioxide adsorption. Molecular simulations suggest that CO2 density in micro and narrow mesopores will be increased at high pressures. This is consistent with the observation that these pores are mainly responsible for the material's high-pressure CO2 capacity. This study provides insights in designing of bio-tar material and further developing for CO2 capture from natural gas. (c) 2020 Elsevier Ltd. All rights reserved.