(595d) Finely Tuned Submicroporous Thin-Film Nanocomposite (TFN) Molecular Sieve Membranes for Water Purification

Water separation membranes formed from state-of-the-art polyamide thin-film composites (TFCs) show relatively low rejections to small neutral contaminants such as boron. The rapid increase in global demand for high purity water for municipal, agricultural, and industrial applications has stimulated substantial research in developing highly selective membranes for water purification. Aiming to improve the selectivity of the current TFC desalination membranes, metal-organic frameworks (MOFs), such as MIL-101(Cr), which have good water stability, high surface area, small particle size, and amine functional groups were successfully synthesized and incorporated into the polyamide selective layer of a TFC membrane to fabricate thin-film nanocomposite (TFN) membranes. Compared to the unmodified benchmark TFC membrane, the incorporation of amine-functionalized MOF nanoparticles during interfacial polymerization not only changed the properties of the polyamide matrix but also reduced the effective pore size of MOF fillers through a crosslinking reaction between the amine functional groups of the MIL-101(Cr) fillers and the trimesoyl chloride (TMC) monomer, thus leading to a significant improvement in membrane selectivity. The best performing TFN membrane showed outstanding rejections to NaCl and small neutral contaminants such as boric acid, which are much higher than those of the benchmark TFC membrane and even better than the state-of-the-art seawater desalination membranes. This study has demonstrated the promising potential of MOF–polymer composite materials for applications related to water purification.