Experimental and modeling study of 6FDA-Durene polyimide/ionic liquid-modified ZIF-8 mixed matrix membranes for CO2 separation

Abstract

Recent membrane research has garnered significant interest in the pursuit of physicochemically stable membranes with outstanding separation capabilities. Introducing inorganic/organic fillers into polymer matrices to create mixed matrix membranes (MMMs) is an effective approach to enhance membrane performance and address the permeability/selectivity trade-off. This study involved the fabrication of a series of MMMs by incorporating [OMIM][PF₆] ionic liquid-modified ZIF-8 as filler into the 6FDA-Durene polyimide (PI) matrix to enhance its physicochemical and separation properties. The pure gas permeation studies were performed on these MMMs with different filler loadings (0–10 wt.%) at 25 °C and 2–10 bar. Extensive characterization methods, such as FESEM, EDX, FTIR, DLS, DSC, TGA, XRD, and Zeta-potential, were utilized to evaluate the synthesized fillers and membranes. Moreover, molecular dynamics (MD) simulation, in conjunction with gas permeation models, and substantiated the exceptional compatibility of ZIF-8/IL with the PI chains. The Sobol method is used to analyze the impact of variable parameters on the efficacy of MMMs. The results indicated that the 6FDA-Durene/5 wt.% ZIF-8/IL membrane shown superior performance in CO₂/CH₄ and CO₂/N₂ separations. The CO₂ permeability rose from 640 Barrer for the pure 6FDA-Durene membrane to 1166 Barrer in the 6FDA-Durene/5 wt.% ZIF-8/IL MMM, representing an increase of approximately 82 %. The CO₂/CH₄ and CO₂/N₂ selectivities of 6FDA-Durene/5 wt. % ZIF-8/IL attained values of 21.45 and 20.48, respectively. The sensitivity analysis reveals that feed pressure significantly influences gas permeability, while filler loading represents the second highest first-order index among the other parameters. In comparison to the pure 6FDA-Durene membrane, the 6FDA-Durene/5 wt. % ZIF-8/IL MMM presents promising potential for further exploration in the advancement of high-performance membranes for gas separation applications.