Coulomb potential, taking LJ parameters for framework atoms and adsorbed molecules from the Universal Force Field (UFF) and TraPPE 49 force field, respectfully. For cross-interactions between unlike atoms, the LJ parameters were approximated using Lorentz-Berthelot mixing rules. A simulation supercell with all three dimensions greater than twice the LJ potential cut-off distance of 12 Å was used to satisfy the minimum image convention.