It has been evaluated that decomposition of carbonates can be used for storing and temperature-upgrading of thermal energy, and that efficient CO2 adsorbents will play an important role in storing the decomposed product CO2. In this study, adsorptivity of CO2 by zeolite 13X and super activated carbon at 100 - 1013 kPa and 287.5 - 573 K were studied. Both adsorbents exhibit an increase in adsorptivity with increase in pressures and with decrease in temperatures. It was found that the adsorptivity data of CO2 by zeolite 13X and super activated carbon can be most accurately represented by Freundlich’s equation. By using Freundlich’s constants, heats of adsorption were estimated and adsorption isosteres were also established on a pressure-temperature diagram in order to evaluate the operating states of the corresponding heat pump system.