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Organic solvent nanofiltration (OSN) offers an energy-efficient alternative to conventional thermal distillation processes for organic solvent separations. However, the fabrication of polymeric OSN membranes with adequate chemical stability in strong polar aprotic solvents remains a remarkable challenge. In this work, chemically robust polyamide thin-film composite (TFC) OSN membranes were fabricated by utilizing an innovative chemical modification of polyimide (PI) nanofiber substrate via one-step crosslinking and thermal cyclodehydration of terephthalic hydrazide (TPDH). The crosslinking and cyclodehydration reaction mechanisms were thoroughly elucidated and the effects of TPDH loading and thermal treatment conditions on solvent resistance and pore structure of the resulting TPDH/PI nanofiber substrates as well as the formation of the polyamide selective layer were systematically studied. The resulting TFC membranes show excellent stability in polar aprotic solvents (i.e., DMF, DMAC, and NMP), and a high DMF permeance of 9.4 L m−2 h−1 bar−1 was achieved with a 99.8% rejection to Rose Bengal at 2.0 bar. The outstanding long-term performance stability revealed the robust structure of the developed TFC OSN membranes. This work demonstrates a facile strategy to address the chemical stability limitations of TFC OSN membranes through a multifaceted yet generalizable approach of chemical crosslinking and thermal cyclodehydration. We believe this strategy can be broadly applied to different substrates, enabling TFC membranes to address a wide variety of unmet OSN needs. (TFC membranes with chemically robust TPDH/PI nanofiber substrates for polar solvent filtration). [Display omitted] • Polyimide (PI) nanofiber substrate was chemically crosslinked by terephthalic dihydrazide (TPDH). • Thermal cyclodehydration further improves the chemical robustness of the crosslinked TPDH/PI nanofiber substrates. • The modified TPDH/PI nanofiber substrates show outstanding stability in polar aprotic solvents. • The resulting polyamide TFC membranes exhibit excellent performance in organic solvent filtration. [ABSTRACT FROM AUTHOR]

Membranes with high permeance, excellent selectivity coupled with adequate solvent resistance are required for organic solvent nanofiltration (OSN) applications. But the "trade-off" relationship between the solvent resistance and permeance remains a critical challenge for polymeric-based thin film composite (TFC) membranes with necessary chemical crosslinking. Herein, a novel facile cyclization modification of polyacrylonitrile (PAN) nanofiber substrate is proposed by a simply thermal treatment and subsequent alkaline hydrolysis, and employed for the fabrication of TFC-OSN membrane for the first time in strong polar aprotic solvent systems. The reaction mechanism involved, solvent resistance and pore structure of PAN nanofiber substrate brought by the modification are investigated. TFC-OSN membrane supported by the modified PAN nanofiber substrate exhibits ultrahigh solvent permeance up to 13.3 L m−2 h−1 bar−1 coupled with a 99.7% rejection in rose bengal/DMF system and a good long-term stability. This study is therefore believed to provide useful guidelines for the development of next-generation OSN membranes. [Display omitted] • A facile cyclization modification of PAN with thermal and alkaline treatment is proposed. • Modified PAN nanofiber substrate shows enhanced resistance in strong polar aprotic solvents. • The substrate with high porosity shows superior pure solvent permeance. • TFC membrane exhibits superior OSN performance to most previous works. [ABSTRACT FROM AUTHOR]