The Henry coefficient and the isosteric heat of adsorption were directly calculated from the methane energy grids using the following equations: where N being the number of grid points, kB being the Boltzmann constant, and T representing temperature (298 K in this work). β is defined as 1/ kBT, and Ei is the energy value at the i th grid point. Additionally, the void fraction was determined as the fraction of grid points whose values are equal or less than 15 kBT.