Ordered mesoporous silica matrices supported ionic liquids for efficient CO2 separation from CO2/CH4 gas mixture: Experimental and theoretical investigation

Global concern over CO2 reduction to avoid global warming has escalated due to alarming CO2 concen-trations in the atmosphere. In this connection, supported-ionic liquids (SILs) have been prepared by phys-ically imbibition of 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) ionic liquid (IL) into ordered mesoporous silica (MS) matrices to design SILs-membranes (SILMs) for gas separation technol-ogy. These SILs were characterized by powder XRD, 29Si NMR, SEM, FTIR, and 1H NMR spectroscopy, N2 sorption, and TGA analyses. FTIR study reveals that vibrational frequencies related to C2mim+ cation ring remain unchanged upon confinement of nanopores of MS whereas Si-O-Si band, Si-O band, and anion band shifted indicating IL interacting with the MS surfaces. Density functional theory (DFT) calculations also explore the structural features of these SILs. SILMs based on Pebax-1657 were also designed using a solution casting technique to evaluate their gas separation performance and characterized using XRD and SEM techniques. C2mimBF4/MCM-48 membrane exhibit higher permeability for CO2 both in single and mixed gas studies. These results were further supported by DFT analysis in terms of complexation ener-gies (Ec) which demonstrates the strong affinity of these SILs membranes towards CO2 and CH4 gases, respectively. Further, a nice correlation was established between the experimental and theoretical findings.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study addresses the global warming issue by preparing supported ionic liquids and designing membranes for gas separation technology, showing strong affinity of these membranes towards CO2 and CH4 gases with a good correlation between experimental and theoretical findings.