In-situ interfacial synthesis of metal-organic framework/polyamide thin-film nanocomposite membranes with elevated nanofiltration performances

Incorporation of nanomaterials in the thin film polyamide (PA) is instrumental to overcome the intrinsic trade-off between permeability and selectivity of polymeric nanofiltration (NF) membranes. However, the universal method of preparing thin film nanocomposite (TFN) NF membranes by directly combining the synthesized nanofillers into PA faces a stubborn issue of poor compatibility for filler-PA, which is adverse to membrane separation. Herein, an in-situ interfacial synthetic strategy was induced in interfacial polymerization (IP) process to prepare TFN membranes with metal-organic framework (MOF) in the PA selective layer. The metal ions and ligands constituting the MOF were dissolved individually in the aqueous and organic phases. MOF particles and the PA layer were simultaneously formed at the liquid-liquid interface. The increment of cross-linking degree confirmed the good compatibility between MOF and PA. Compared with the thin film composite (TFC) membrane, the acquired TFN-1 membrane exhibited 100 % enhancement of pure water permeance (from 10.0 to 20.6 L m−2 h−1 bar−1) due to the markedly reduced thin film thickness. Meanwhile, the rejection of rhodamine B (99.9 %) and Na2SO4 (96.5 %) for TFN membrane were higher than those of TFC membrane (97.2 % and 95.6 %), respectively. The TFN membrane exhibited long-term stability without deterioration. The in-situ interfacial synthesis of the MOF/PA layer provides a new avenue in TFN membrane fabrications.