Capturing CO2selectively from flue gas and
natural
gas addresses the criteria of a sustainable society. In this work,
we incorporated an ionic liquid (IL) (1-methyl-1-propyl pyrrolidinium
dicyanamide, [MPPyr][DCA]) into a metal organic framework (MOF), MIL-101(Cr),
by wet impregnation and characterized the resulting [MPPyr][DCA]/MIL-101(Cr)
composite in deep detail to identify the interactions between [MPPyr][DCA]
molecules and MIL-101(Cr). Consequences of these interactions on the
CO2/N2, CO2/CH4, and CH4/N2separation performance of the composite were
examined by volumetric gas adsorption measurements complemented by
the density functional theory (DFT) calculations. Results showed that
the composite offers remarkably high CO2/N2and
CH4/N2selectivities of 19,180 and 1915 at 0.1
bar and 15 °C corresponding to 1144- and 510-times improvements,
respectively, as compared to the corresponding selectivities of pristine
MIL-101(Cr). At low pressures, these selectivities reached practically
infinity, making the composite completely CO2-selective
over CH4and N2. The CO2/CH4selectivity was improved from 4.6 to 11.7 at 15 °C and 0.001
bar, yielding a 2.5-times improvement, attributed to the high affinity
of [MPPyr][DCA] toward CO2, validated by the DFT calculations.
These results offer broad opportunities for the design of composites where ILs are incorporated into
the pores of MOFs for high performance gas separation applications
to address the environmental challenges.