Résumé
The adsorption of carbon dioxide and its separation from mixtures with methane using the recently synthesized SIFSIX-2-Cu-i metal-organic framework has been systematically studied by employing a variety of molecular simulation techniques. Quantum density functional theory calculations have been combined with force-field based Monte Carlo and molecular dynamics simulations in order to provide a deeper insight on the molecular-scale processes controlling the thermodynamic and dynamic adsorption selectivity of carbon dioxide over methane, giving particular emphasis to the mechanisms underlying the diffusion of the confined molecules in this hybrid porous material. The diffusion process was revealed to be mainly controlled by both (i) the residence dynamics around some specific interaction sites of the fluorinated metal-organic framework and (ii) the dynamics related to the process where faster molecules overtake slower ones in the narrow one-dimensional channel of SIFSIX-2-Cu-i. We further unveiled a 1 dimensional diffusion behavior of both carbon dioxide and methane confined in this small pore MOF where single file diffusion is not observed.