Thin-Film Nanocomposite Membranes Containing Water-Stable Zirconium Metal–Organic Cages for Desalination

The introduction of porous nanofillers into the polyamide selective layer of thin-film composite membranes is a promising strategy towards improved water flux and salt rejection for reverse osmosis membranes. However, the incorporation of filler particles is constrained by the poor compatibility between particle fillers and a polyamide layer. In this study, we report the rationally chosen zirconium metal–organic cages (Zr-MOCs) with ideal stability, solubility, and porosity characteristics as molecular fillers for thin-film nanocomposite (TFN) membranes. In addition, we use monoamino compounds to fine-tune the structure of the polyamide selective layer and the performance of the TFN membranes following the "defective ligand" strategy. The optimized TFN membranes exhibit up to a fourfold increment in water flux without compromising the salt rejection, underlining the promising potential of Zr-MOCs as molecular fillers in TFN membranes.