This paper describes the development of carbon-based adsorbents for CO2 separation in integrated gasification combined cycle (IGCC) processes for energy generation and hydrogen production. The research presented forms part of a Research Fund for Coal and Steel funded project “Hydrogen separation in advanced gasification processes” (HYDROSEP) with the ultimate aim of developing technologies to reduce the costs for the capture of CO2 when compared to existing absorption processes. A range of carbon adsorbents were developed by MAST Carbon. They present significant microporosity and in some cases also meso or macroporosity. CO2 adsorption isotherms have been determined using a dual limb differential pressure apparatus under realistic operating conditions. CO2 and H2 high pressure adsorption isotherms at room temperature have also been evaluated in a high pressure adsorption balance. Maxima CO2 uptakes of 58 wt.% at 3 MPa and H2 uptakes of 0.3 wt.% at 4 MPa were obtained. The significant differences observed in CO2 and H2 adsorption at high pressures showed the high selectivity for CO2 of the tested MAST Carbon adsorbents.