CO2 selective metal organic framework ZIF-8 modified through ionic liquid encapsulation: A computational study

Nano-scale porous solids are alternate candidates for CO2 handling towards the development of materials for post-combustion CO2 capture with low energy demands and milder operating conditions. Zeolitic imidazolate framework-8 (ZIF-8) is one of the most investigated Metal Organic Frameworks (MOFs) for separation of gas mixtures. In this work, we investigate a new approach of tailoring MOF separation efficiency, by confining pairs of [bmim(+)][Tf2N-] ionic liquid (IL) in the cages of ZIF-8 (IL@ZIF-8). Molecular force fields, developed by the authors for both the ZIF-8 framework and the [bmim(+)][Tf2N-] IL, are used in molecular simulations of the system. Monte Carlo simulations are used for sorption of CO2/CH4 and CO2/N-2 mixtures computations. The results show an increase of the CO2 sorption due to the presence of the IL, which increases CO2 selectivity and capacity dramatically. Recently reported experiments agree with our findings. Moreover, we explore how CO2 selectivity and capacity varies with IL composition in the IL@ZIF-8 complex, as means to define an optimum IL composition in terms of the separation efficiency. (C) 2018 Elsevier B.V. All rights reserved.