Regulating interfacial polymerization via a hybrid PVA/BCN nanocomposite interlayer for high-performance reverse osmosis membranes

A hybrid polyvinyl alcohol (PVA)/boron carbon nitride (BCN) nanocomposite interlayer was developed to regulate interfacial polymerization (IP) kinetics and enhance the separation performance of thin-film composite (TFC) reverse osmosis membranes. The hydrophilic PVA interlayer moderated m -phenylenediamine (MPD) diffusion, suppressed polyamide (PA) intrusion into substrate pores, and promoted the formation of a thinner and more compact PA selective layer. Incorporation of two-dimensional BCN nanosheets further intensified the monomer-regulation effect of the interlayer and introduced additional low-resistance transport pathways within the interlayer. The optimized i-TFN-0.05 membrane (containing 0.05 wt% of BCN nanosheets in PVA matrix) achieved a high water permeance of 4.1 L.m⁻².h⁻¹.bar⁻¹ with 98.6% NaCl rejection, outperforming pristine TFC and commercial benchmark membranes. Surface characterization revealed enhanced hydrophilicity, reduced roughness, and a more negative surface charge, which collectively contributed to improved fouling resistance and high flux recovery. Long-term operation further confirmed the structural stability of the hybrid interlayer system, demonstrating its strong potential for durable, high-performance desalination applications.