Synergistic Effect of 2D ZIF Loading and Ionic Liquid Modification on Improving Gas Separation Performance of PES-Based Mixed Matrix Hollow Fiber Membrane

This study reports the synthesis of 2D leaf-like ZIF-L and its modification using [BMIM][BF4] ionic liquid (IL). The nanosheet was then embedded up to 5 wt% into the polyethersulfone (PES) to form mixed matrix hollow fiber membrane (MMHFM) to separate CO2/N2 gases. IL altered the surface charge of the ZIF-L which results in a more uniform dispersion of ZIF-L in the polymer matrix and minimizes the ZIF-L agglomeration on the lumen side. The filler–polymer interaction was improved as suggested by the TGA data. An evaluation of the performance of the MMHFM indicated that the synergistic effect between the filler modification and its loading is crucial in improving the performance of the membrane. The incorporation of unmodified ZIF-L resulted in a significant loss of selectivity at low loading (≥ 1 wt%). Meanwhile, permeance and selectivity trade-off are absent up until 2.5 wt% IL@ZIF-L. Besides, better ZIF-L dispersion and enhanced interaction between the filler and polymer are the factors that improved the separation performance of the MMHFM, hence highlighting the vital role of IL in the system. At the feed pressure of 2 bar, PES/IL@Z0.5 improved the CO2 permeance and ideal CO2/N2 selectivity by 106% and 86%, respectively, relative to the pristine.