To assuage global climate change concerns with greenhouse gas generation, capturing and sequestering CO 2 emission is one of the promising methods. The current strategies are implementation of sequestration options from saline aquifers and depleted oil and gas reservoirs to unminable coal seams and abandoned coal mines. Along with the storage capacity of reservoirs, the sealing integrity of caprock and potential changes in this integrity is one of important factors due to the interaction with CO 2. Clay mineral is one of constituent of coal mineral matter and it is also a major mineralogy of shale which is used as cap rocks for storage. It has a chemical composition based on phyllosilicate crystalline phases with incorporated metal cations and other impurities such as water. Its structure can expand for better pore accessibility and contract to trap so that small molecules trapping can be induced. In this study, gas adsorption characteristics on three kinds of clay minerals were measured and compared from subcritical to supercritical conditions to evaluate the CO 2 storage potential of these materials under reservoir conditions. In addition, the structural change caused by CO 2 sorption was observed from BET results comparison between raw material and CO 2 adsorbed one after the experiment.