Thermal energy storage capacity of working fluid can be enhanced by using energy conversion of adsorption/desorption process of working fluid in nanoporous materials. Molecular simulation including molecular dynamics and grand canonical Monte Carlo are employed to investigate the energy storage of CO2/IRMOF-1 (isoreticular metal organic framework) nanoparticle mixture. The results show that the calculated heat capacity by molecular dynamics simulation agrees with experimental data. The thermal energy storage capacity of CO2 increases with the increase of mass ratio of IRMOF-1 nanoparticles. IRMOF-1 is conducive to enhance the capacity of thermal energy storage when the surrounding pressure is low. (C) 2018 Elsevier Ltd. All rights reserved.