MOF nanoparticles of MIL-68(Al), MIL-101(Cr) and ZIF-11 for thin film nanocomposite organic solvent nanofiltration membranes

Abstract

Nanoparticles (NPs) of MOFs MIL-101(Cr), MIL-68(Al) and ZIF-11 with sizes of 70, 103 and 79 nm, respectively, have been used in the development of thin film nanocomposite (TFN) membranes. Such membranes were synthesized with an ultrathin polyamide layer, in which NPs are embedded, about 100–150 nm thick on top of a polyimide P84® asymmetric support. Several important effects have been studied in the synthesis of the membranes for their application to organic solvent nanofiltration (OSN): the effect of the non-solvent bath, the chemical post-treatment, the concentration of precursors for interfacial polymerization and the polymerization time. The influence of different solvents (water, methanol, acetone and THF) and solutes (Acridine Orange, Sunset Yellow and Rose Bengal) on the OSN has also been studied. The hydrophilic character of the membrane and the solvent-membrane and solute–membrane interactions are shown to be the most important parameters affecting the performance of the composite membranes. A maximum permeance of 6.2 L m⁻² h⁻¹ bar⁻¹ and a rejection above 90% was obtained from the combination of ZIF-11 and a post-treatment via filtration with dimethylformamide.