Investigating polarization effects of CO2 adsorption in MgMOF-74

MgMOF-74 is a promising candidate for a variety of gas separation applications, e.g., carbon capture and natural gas sweetening due to its high CO2 uptake capacity and its favorable selectivity toward CO2. Motivated by its promising properties, MgMOF-74 has been extensively studied both experimentally and computationally. Experimentally determined adsorption isotherms show an inflection at a loading of approximately one CO2 molecule per magnesium ion due to strong adsorption sites close to the ions. It is a great challenge to accurately reproduce this behavior in molecular simulations. In this study, we explicitly consider polarization between the adsorbed CO2 molecules and the framework of MgMOF-74 via the induced point dipole method. Back-polarization is neglected to achieve reasonable simulation times. To account for implicitly incorporated polarization, we rescale the Lennard-Jones energy parameters with respect to the atomic polarizabilities. A series of Monte Carlo simulations of CO2 in MgMOF-74 is conducted. The computed CO2 adsorption isotherm is in good agreement with experimental measurements and previous simulation results using a DFT-derived force field. This indicates that polarization is important for describing the adsorption of CO2 in MgMOF-74. The direct inclusion of polarization will lead to force fields with better physical justification and transferability.