Electrostatic Interactions Impact On CO2 Adsorption In Metalorganic Framework with Open Metal Sites

Metalorganic frameworks (MOFs) has shown great potential for CO2 capture. The difficulties of synthesis and the limited quantities produced make molecular simulation techniques very attractive to assist in investigations on the fundamentals of the adsorption process. Force fields are a central tool to molecular modeling and efforts have been made to implement adequate force fields to specific MOFs structures but the charge assignment is even a challenge task. In this study equilibrium variables related to the implicit use of sorbate-sorbate and/or sorbate-framework electrostatic interaction are investigated. Three commercial  MOFs structures (Cu-BTC, ZIF-8 and MIL-100Fe) with and without open metal sites are used as models. We had observed that sorbate-sorbate electrostatic interactions are sufficient to predicting adsorption isotherms in MOFs without open sites however sorbate-sorbate and sorbate-framework electrostatic interactions are essential for predicting CO2 adsorption isotherms in metalorganic framework with open metal sites. A discussion about charge equilibration and DFT methods for charge assignment is also presented.