Construction of selective gas permeation channels in polymeric membranes using nanocage tuned ionic liquid/MIL-53 (Al) filler nanoparticles for effective CO2 separation

Abstract

Polymeric membranes with metal-organic frameworks (MOFs) holds great potential for gas separation. However, finely tailoring the adhesion between MOFs and polymer matrices is crucial in reducing the membranes defective structure. The partial inorganic structure of MOFs limits the interaction with the polymer matrix, which tends to agglomerate on the membranes. Herein, an interfacial strategy is reported by post-synthetic functionalization of MIL-53 (Al) with ionic liquids (ILs) to construct IL@MIL-53 (Al) composite to improve interfacial interaction among filler and polysulfone (PSf) matrices. At 2 wt% of IL@MIL-53 (Al), the composite membranes tensile strength and % elongation were enhanced by about 66.13 and 97.40% compared to the neat PSf membrane. The intimate contact between IL@MIL-53 (Al) and PSf matrices renders uniform dispersion evident from morphological studies. The gas permeation properties were evaluated for carbondioxide (CO₂), nitrogen (N₂), methane (CH₄) gases. At 2 wt% of MIIL-53 (Al) nanofiller, the CO₂ permeance was found to be 37.56 ± 0.63 GPU which was significantly higher than the neat PSf membrane. Besides, the CO₂ permeance of the PSf/2% IL@MIL-53 (Al) membrane was noted to be 34.23 ± 0.68 GPU, whereas the CO₂/CH₄ and CO₂/N₂ selectivities were 48.64 and 49.19% higher than the neat membrane. As the pressure increased from 2 to 10 bar, the CO₂, N_2, and CH₄ gas permeances in composite PSf membranes were decreased, whereas the CO₂/N₂ and CO₂/CH₄ selectivities were observed to be increased. The introduction of ILs into the MOFs pores will tune pore size with the enhanced adsorption selectivity due to its high CO₂ solubility and affinity of ILs. ILs functionalization on the cores of the MIL-53 (Al) structure is an effective strategy, which opens up the selection to a broad range of fillers in the aspect of commercialization.