Hierarchical porous graphene-based carbons (HPGCs) have been prepared by a simple carbon dioxide activation of graphite oxide. The effects of activation temperature on the structural and textural properties as well as gas adsorption capacities of the resultant carbons have been investigated. The HPGCs showed hierarchically micro-meso-macroporous structures, high specific surface areas of up to 532 m(2) g(-1), and large pore volumes of up to 1.67 cm(3) g(-1). Moreover, the HPGC materials were demonstrated to be efficient for CO2 and H-2 adsorption. The HPGC-850, which was obtained after two hours of activation at 850 degrees C, exhibited the highest adsorption capacities of 7.74 wt% (1.76 mmol g(-1)) at 273 K and 1 bar for CO2 and of 0.75 wt% (3.76 mmol g(-1)) at 77 K and 1 bar for H-2. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.