Investigation of CO2 capture using acetate-based ionic liquids incorporated into exceptionally porous metal–organic frameworks

Abstract

The potential advantage of using supported ionic liquids (SILs) for CO2 capture applications has been investigated in this work. The impregnation of 1-ethyl-3-methylimidazolium Acetate [emim][Ac] into two voluminous metal–organic frameworks (MOF-177 and MIL-101) is evaluated using different synthesis methods. The performance of the composite sorbents for CO2 capture has been evaluated using various characterization techniques. The successful incorporation of [emim][Ac] into the pores of MOF-177 and MIL-101 have been confirmed using thermogravimetric analysis and Fourier transform infrared spectroscopy results. Furthermore, the porosity of the as-synthesized samples using different synthesis methods have been measured using N2 adsorption experiments to evaluate the changes in the specific surface areas and pore volumes upon the introduction of [emim][Ac] to the support materials. A significant decrease in the porosity was realized for the [emim][Ac]-confined samples especially when using wet impregnation synthesis method compared to the dry mixing approach. The crystal structures of the MOF-177 and MIL-101 were found to be maintained after the synthetic steps, with some reductions in the X-ray diffraction peak intensities. No improvements in the CO2 uptakes could be achieved for the MIL-101 samples using both synthesis strategies, whereas the [emim][Ac]@MOF-177 samples prepared using wet impregnation method, has shown a remarkable enhancement in the CO2 capacity up to 0.3 mmol/g at 0.15 bar and 303 K. Moreover, the adsorption kinetics in MOF-177 based samples was found to be significantly fast as depicted from the first order rate constant values. The [emim][Ac]@MOF-177 samples exhibited a substantially stable cyclic adsorption–desorption performance up to 10 successive cycles with a considerably fast desorption kinetics.