Piperazine-modulated bis-tris-based polyester-amide nanofilm for high-performance nanofiltration membrane

Polyester-amide (PEA) membranes combine the chemical stability of polyester (PE) with the highly cross-linked structure of polyamide (PA), achieving a synergistic breakthrough in selectivity, permeance, and stability. This study presents a strategy that employs a bulky polyhydroxy monomer (Bis(2-hydroxyethyl) amino-tris(hydroxymethyl)methane, Bis-Tris) and a highly reactive amine monomer (PIP) as combined aqueous-phase monomers for interfacial polymerization. A systematic comparison of the structural and physicochemical properties of PIP-PA, Bis-Tris-PE, and Bis-Tris-PIP PEA nanofilms demonstrates that the PEA nanofilm exhibits a unique microstructure combining the porous characteristics of PE with the nodular morphology of PA, along with appropriate thickness, surface charge, hydrophilicity, and pore size. The B 0.3 PIP 0.3 membrane exhibits outstanding overall performance, achieving a water permeance of 16.8 L·m -2 ·h -1 ·bar -1 and a Na 2 SO 4 rejection of 99.6%, both superior to the NF 270 membrane. Moreover, it integrates the alkaline resistance characteristic of PA with the chlorine resistance of PE, along with notable pressure resilience and long-term stability. Molecular dynamics simulations revealed a more uniform and controllable monomer diffusion in the Bis-Tris/PIP co-monomer system. Molecular crosslinked models further identified free volume among the three membranes, offering a theoretical basis for their performance differences. This study underscores the promise of a multifunctional co-monomer strategy in tailored NF membranes. • Co-monomer strategy enables high-performance polyester-amide membranes. • Synergistic use of polyhydroxy Bis-Tris and highly reactive PIP. • Mechanistic insight from comparative analysis of PE, PA, and PEA membranes. • Outstanding performance was achieved with 16.8 L·m −2 ·h −1 ·bar −1 and 99.6% rejection. • Systematic characterization and MD simulations revealed the underlying mechanism.