Polyamide Membranes with Net-Like Nanostructures Induced by Different Charged MOFs for Elevated Nanofiltration

Fabricating nanostructured and nanomaterial enhanced polyamide (PA) selective layer are the trend for next-generation thin-film composite (TFC) membranes for elevated performance. However, the mechanism of how nanomaterials affect the formation of a PA layer remains unclear. Here, we synthesized a series of UiO-66 metal-organic frameworks (MOFs) with different particle zeta-potentials and incorporated these MOFs in either aqueous or organic phase for interfacial polymerization. PA layers with different morphology, surface chemistry and formation mechanism are obtained in the presence of MOFs with varied zeta-potentials. Doping UiO-66 with neutral surface charge in the aqueous phase and UiO-66 with highly positive charge in the organic phase will both lead to the formation of net-like nanostructure. These nanostructures endow the thin-film nanocomposite (TFN) membranes with pure water flux up to 58.5 L m(-2) h(-1) at 0.6 MPa and Na2SO4 rejection of 99.6%, which is similar to-67% higher than the TFN membrane with a nodular morphology. We believe this work establishes a good understanding for facile fabrication of high-performance TFN membranes with more favorable nanostructures.