Investigation of CO2 adsorption in Faujasite systems: Grand Canonical Monte Carlo and molecular dynamics simulations based on a new derived Na+–CO2 force field

Both Grand Canonical Monte Carlo and Molecular Dynamics simulations have been carried out to gain further insight into the CO2 adsorption process at the microscopic scale in NaX and NaY Faujasites. A new Na+–CO2 force field was derived using quantum calculations performed on realistic cluster directly excised from the periodic structure. Both the methodology and the force field were validated by a good agreement between both the simulated isotherms and the evolution of the differential enthalpies of adsorption as a function of adsorbate coverage and those previously obtained by Microcalorimetry. In addition, the microscopic mechanisms of CO2 adsorption in both systems, consistent with the trends observed for the differential enthalpies of adsorption, were proposed. It was observed that two different types of adsorption behaviour exist for NaY and NaX, and can be defined by involving one (SII cations) or two (SIII′ and SII cations) preferential adsorption sites respectively.