Coordination-crosslinked polyimide supported membrane for ultrafast molecular separation in multi-solvent systems

Substrate modification of thin film composite (TFC) membranes by various crosslinkers is generally required for organic solvent nanofiltration (OSN) application, to enhance the membrane stability and solvent resistance, which however leads to the permeance decline. In this contribution, coordination-crosslinked polyimide substrate is developed for the first time, which is different with those covalently-crosslinked substrates, and achieves the enhanced solvent resistance, improved hydrophilicity and optimized porous microstructure simultaneously. The effects of the alkaline coagulation bath, subsequent ion exchange, and further solvent activation are investigated. The resultant TFC membrane breaks through the typical permeability-selectivity trade-off of OSN membranes successfully, exhibiting an astonishingly superior solvent permeance (1.5–2 times the highest data) (65.2 LMH/bar for methanol, 33.1 LMH/bar for ethanol and 59.1 LMH/bar for acetone) to previously reported polymeric-based TFC OSN membranes with a competitive solute rejection (>98% for Rose Bengal). This study is believed to provide a new orientation in the development of the desirable substrate for the high-performance OSN composite membrane and other separation applications.