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

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.