Highly permeable ionic liquid membrane by both facilitated transport and the increase of diffusivity through porous materials

Abstract

Ionic liquid membranes have showed low permeance, due to high viscosity when utilized for gas separation, limiting their practical application despite advantages such as high thermal stability and high CO₂ selectivity. In this study, Cu nanoparticles generated by redox reduction with Fe²⁺ ions and porous KIT-6 were utilized for high selectivity and as a permeable membrane. When positively polarized Cu nanoparticles were generated and porous KIT-6 materials were incorporated into ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM BF₄), the selectivity for CO₂/N₂ and CO₂/CH₄ of the composite membrane was largely enhanced to 16.4 and 23.4, respectively while neat BMIM BF₄ was 5.0 and 4.8, respectively. Furthermore, the CO₂ permeance was also enhanced from 17 to 50.7 GPU, compared to the neat BMIM BF₄ membrane. These enhancements of separation performance is attributed to both the facilitated transport by polarized Cu NPs and the increase of diffusivity by porous materials.