Effect of immobilizing ionic liquid on amine-functionalized MIL-101(Cr) incorporated in Matrimid membranes for CO2/CH4 separation

Immobilizing an ionic liquid (IL) on a metal-organic framework (MOF) is proposed as a novel selective and CO2 facilitated transport material to improve gas perm-selectivity and plasticization pressure of Matrimid-based mixed matrix membranes (MMM) for CO2/CH4 separation. NH2-MIL-101(Cr) was synthesized and then impregnated with 1-butyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide ([Bmim] [Tf2N]) to prepare IL@NH2-MIL-101(Cr). The particles were analyzed by X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, and scanning/transmission electron microscopy (SEM/TEM). The particles were then dispersed in Matrimid to prepare MMM with 3, 5, and 7 wt.% contents. The membranes microstructure was investigated by FTIR and XRD, and the uniformity of MOF distribution was examined by SEM. Differential scanning calorimetry (DSC) displayed an increase in glass transition temperature (T-g) for the MMM associated with the polymer chains rigidification in the polymer/filler interphase. Permeation experiments showed that maximum separation performance was found for the MMM containing 7 wt.% IL@NH2-MIL-101 with increased CO2 permeability (162%) and CO2/CH4 selectivity (224%) over pristine Matrimid. This MMM increased plasticization pressure of the Matrimid membrane from 12 to 25 bar. Tensile strength and Young's modulus of the optimum MMM were 25% and 37% higher than those of pristine Matrimid membrane, respectively.

Automated summary

Immobilizing an ionic liquid on a metal-organic framework is proposed as a novel approach to improve gas permeability and selectivity in CO2/CH4 separation. The resulting mixed matrix membranes showed increased CO2 permeability and selectivity, decreased plasticization pressure, and enhanced mechanical properties compared to pristine Matrimid membrane.