Intermolecular cross-linked polymer of intrinsic microporosity-1 (PIM-1)-based thin-film composite hollow fiber membrane for organic solvent nanofiltration

Organic solvent nanofiltration (OSN) is a membrane-based organic solution separation process that has emerged as a viable alternative to energy- and solvent-intensive separation processes. Polymers of intrinsic microporosity (PIMs) are the targets of recent active research on OSN membrane materials because of their unique physicochemical properties, such as solution processability, chemical tunability, robust porosity, and high thermal stability. However, applying PIMs-based membranes in practical OSN applications is still challenging because of their limited organic solvent stability and inevitable decrease in performance. Meanwhile, despite the potential of thin-film composite hollow fiber membranes for OSN, only a few studies have been reported to date. In this study, we fabricated a PIMs-based thin-film composite hollow fiber membrane by dip-coating and improved its organic solvent stability by intermolecular cross-linking. The membrane exhibited pure ethanol permeance of 10.9 LMH/bar and a molecular weight cut-off of 952 g/mol in ethanol. The membrane displayed stable dye rejection performance (>95%) even after immersion in ethanol, acetone, and toluene for seven days. This study demonstrates that intermolecular cross-linking between PIMs polymer chains can improve the organic solvent stability of PIMs-based membranes and provides a desirable strategy to fabricate feasible organic solvent stable PIMs-based thin-film composite hollow fiber membranes for OSN applications.