Thermally Triggered Self-Healing Polyamide Nanofiltration Membranes via Diels–Alder Crosslinking

Nanofiltration (NF) membranes are critical for seawater desalination, wastewater treatment, and ion separation. However, conventional polyamide membranes suffer from irreversible damage, resulting in performance decline and increased operational costs. Developing self-healing PA-based NF membranes remains a major challenge. Herein, we fabricate a high-permeability, self-healing NF membrane via interfacial polymerization (IP) using thermally reversible Diels-Alder (DA) bonds to enable damage recovery. A furan-functionalized polyethylenimine was synthesized as the aqueous monomer, whereas 6-maleimidohexanoyl chloride and trimesoyl chloride served as organic monomers. During IP, acyl chloride formed robust amide bonds with amines, while DA reactions between maleimide and furan groups enabled self-healing. The membrane achieved a water flux of 36.5 L m⁻² h⁻¹, >95% Na₂SO₄ rejection, and with a molecular weight cutoff (MWCO) of 561 Da. After thermal repair, the damaged membrane recovered 88% Na₂SO₄ rejection, and the MWCO is maintained at 857 Da. This work presents a promising strategy to improve the performance and durability of PA NF membranes.