For classical force field calculations, framework atoms were modeled using the universal force field (UFF), with point charges assigned based on the density derived electrostatic and chemical (DDEC) scheme. If the .cif file for a structure contained pre-defined charges, these values were retained without further modification. For guest molecules, specifically CO2 and H2O, the TraPPE 90 and SPC/E 91 force fields were employed, respectively.