This study reports an improved method for activating asphalt to produce ultra-high surface area porous carbons. Pretreatment of asphalt (untreated Gilsonite, uGil) at 400 °C for 3 h removes the more volatile organic compounds to form pretreated asphalt (uGil-P) material with a larger fraction of higher molecular weight π-conjugated asphaltenes. Subsequent activation of uGil-P at 900 °C gives an ultra-high surface area (4200 m2 g−1) porous carbon material (uGil-900) with a mixed micro and mesoporous structure. uGil-900 shows enhanced room temperature CO2 uptake capacity at 54 bar of 154 wt% (35 mmol g−1). The CH4 uptake capacity is 37.5 wt% (24 mmol g−1) at 300 bar. These are relevant pressures in natural gas production. The room temperature working CO2 uptake capacity for uGil-900 is 19.1 mmol g−1 (84 wt%) at 20 bar and 32.6 mmol g−1 (143 wt%) at 50 bar. In order to further assess the reliability of uGil-900 for CO2 capture at elevated pressures, the authors study competitive sorption of CO2 and CH4 on uGil-900 at pressures from 1 to 20 bar at 25 °C. CO2/CH4 displacement constants are measured at 2 to 40 bar, and found to increase significantly with pressure and surface area.