Tailoring the pore size of intermolecular cross-linked PIMs-based thin-film composite hollow fiber membranes using different length cross-linkers for organic solvent nanofiltration

The recovery and recycling of solvents and resources from waste solutions generated by the downstream processes of various industries are essential for achieving sustainable development. Membrane-based organic solvent nanofiltration (OSN) technology has received considerable attention as a feasible approach for recovering solvents and resources. However, for OSN, tailoring the pore size of membrane is a key challenge because different industrial processes require the removal of solutes of varying sizes. In this study, the pore sizes of thin-film composite hollow fiber membranes based on an intermolecular cross-linked polymers of intrinsic microporosity were tailored using four linear diamines of varying lengths as cross-linkers. As the length of the cross-linker increased, the fabricated membranes exhibited an increase in mean pore diameters, ranging from 1.01 to 1.35 nm, and showed narrower pore size distributions. This is because as the length of the cross-linker increases, it leads to the formation of longer intermolecular cross-links and a higher proportion of fully reacted diamines (intermolecular cross-links) compared to partially reacted diamines. The membrane with 1,8-diaminooctane as a cross-linker exhibited excellent homogeneous catalyst recycling performance for BINAP-Ru(II) solutions. The fabricated membrane showed ethanol and methanol permeances of 4.6 and 14.0 L m(-2) h(-1) bar(-1), respectively, with over 98% BINAP-Ru(II) rejection for 12 h. Thus, the developed membrane is promising for solvent and resource recovery from waste solutions of various industries.