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.