Performance Evaluation of Supported Ionic Liquid Membranes (SILMs) Derived from Optimized PES/PDMS/ZIF-L Composites for CO2 Separation

This study proposes the fabrication of metal–organic framework (MOF)-based supported ionic liquid membranes (SILMs) to separate CO2 selectively. This report consists of two main parts; the first part focuses on optimizing polyethersulfone/poly(dimethylsiloxane)/zeolitic imidazolate framework-L (PES/PDMS/ZIF-L) composite membrane fabrication to improve CO2 permeance and selectivity simultaneously. The optimization process was carried out by the Box–Behnken design (BBD). At the optimized conditions (4.70 wt % PDMS, 5 mm/s withdrawal speed, 73.5 s dipping time, and 1.5:1 ZIF-L:PDMS ratio), the composite membrane recorded 6.61 GPU of CO2 permeance. Furthermore, the CO2/N2 and CO2/CH4 selectivities were 20.20 and 6.19, respectively. The second part of this report focuses on developing the supported ionic liquid membrane (SILM) by altering the optimized PES/PDMS/ZIF-L membrane. The SILM fabricated in this study undergoes a distinct fabrication method where the ionic liquid ([BMIM][BF4]) was impregnated in the ZIF-L instead of the porous support. Such a fabrication method was attempted due to the flexible structure of ZIF-L as a response to heat and able to immobilize the IL. As a result, SILM performed effectively as the CO2 permeance increased to 9.96 GPU at CO2/N2 and CO2/CH4 selectivities of 44.97 and 30.77, respectively. It is hypothesized that the enhancement of performance was achieved due to the synergy between the ZIF-L and IL, as revealed in this article.