Improving Gas Separation Performance of ZIF-8 by [BMIM][BF4] Incorporation: Interactions and Their Consequences on Performance

Abstract

Gas separation performance of the zeolitic imidazolate framework (ZIF-8) was improved by incorporating an ionic liquid (IL), 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). Detailed characterization based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed that the morphology of ZIF-8 remains intact upon IL incorporation up to 28 wt %. Thermogravimetric analysis indicated the presence of direct interactions between the IL and metal organic framework (MOF). FTIR spectroscopy illustrated that the anion of the IL was shared between the imidazolate framework and [BMIM]+ cation. Adsorption isotherms of CO2, CH4, and N2 measured for pristine ZIF-8 and IL-loaded ZIF-8 samples, complemented by grand canonical Monte Carlo (GCMC) simulations, showed that these interactions influence the gas uptake performance of ZIF-8. CH4 and N2 uptakes decreased in the whole pressure range, while CO2 uptake first increased by approximately 9% at 0.1 bar in 20 wt % IL-loaded sample and then d...