Vapor-phase crosslinked mixed matrix membranes with UiO-66-NH₂ for organic solvent nanofiltration

In this work, a series of mixed matrix membranes (MMMs) containing nano-size amine-functionalized UiO-66 particles were vapor-phase crosslinked by tris (3-aminopropyl) amine (TAPA) and investigated for organic solvent nanofiltration (OSN) applications. A thin dense layer was successfully formed on top of MMMs which improved solute selectivity in isopropanol (IPA). By manipulating (1) the size and loading of UiO-66-NH₂ nanoparticles in dope solutions, and (2) the temperature and duration of the TAPA vapor crosslinking reaction, we have fabricated a membrane with a 99.2% rejection towards negatively charged Rose Bengal (RB, Mw= 1017 gmol⁻¹) in IPA and a pure IPA flux of 11.5 Lm⁻² h⁻¹ at 10 bar. Interestingly, the optimal composite membrane developed in this study shows impressive rejections towards positively charged dyes possibly because of electrostatic repulsion (e.g., Donnan exclusion). In addition, the optimized TAPA vapor-phase crosslinked MMMs display stable performance in various organic solvents and the 14-day rejection test. To our best knowledge, this is the first report on organic solvent nanofiltration MMMs made from the vapor-phase crosslinking modification. This modification method may have great potential to develop next-generation OSN membranes for the separation of organic solvents and solutes in pharmaceutical and food industries.