Metal–Organic Framework Nanocomposite Thin Films with Interfacial Bindings and Self-Standing Robustness for High Water Flux and Enhanced Ion Selectivity

Abstract

Metal-organic framework (MOF)-based materials are promising candidates for a range of separation applications. However, the fabrication of self-standing MOF-based thin films remains challenging. Herein, a facile solution casting strategy is developed for fabricating UiO-66 nanocomposite thin films (UiO66TFs) with thicknesses down to ∼400 nm. Nanosizing UiO-66 and incorporating sulfonated polysulfone additives render high dispersity and interfacial bindings between MOFs and polymer matrices, so UiO66TFs are more mechanically robust and thermally stable than their pure-polymer counterparts. Enhanced microporosity with sub-nanometer pore sizes of the self-standing membranes enables the direct translation of UiO-66-based sorption and ion-sieving properties, thus increasing water flux and separation performance (NaSO rejection of 94-96%) under hydraulic pressure-driven processes and eliminating internal concentration polarization in osmotic pressure-driven processes. Enhanced separation performances are achieved with water/NaSO permselectivity of 13.5 L g and high osmotic water permeability up to 1.41 L m h bar, providing 3-fold higher water/NaSO permselectivity and 56-fold-higher water flux than polymer membranes for forward osmosis.

Homochiral MOF–Polymer Mixed Matrix Membranes for Efficient Separation of Chiral Molecules

“…However, with the increase of the MOF loading from 20 to 30 wt %, the ee value of MIL‐53‐NH‐ l ‐His_30% membrane declined to 71 %. This might be attributed to the partial aggregation of the MOF particles creating more interfacial voids (Figure S14), which leads to the formation of nonselective diffusion pathways through the membrane, resulting in the reduction of selectivity …”

A thin film nanocomposite membrane with pre-immobilized UiO-66-NH2 toward enhanced nanofiltration performance

“…As a prototype Zr-MOF, UiO-66 has displayed interesting physical and chemical characteristics for the preparation of highly water-stable MOF membranes for liquid separation. [22][23][24] The highly regular structure of UiO-66 with the aperture size of about 6.0 A, 25,26 which is located between H 2 O (2.6 A) and hydrated ions (e.g. Na + 7.2 A, Mg 2+ 8.6 A, SO 4 2À 7.6 A, Cl À 6.6 A), is promising for achieving high ux and sustains high salt rejections by ionic sieving.…”

Metal–Organic Framework Thin Films: Fabrication, Modification, and Patterning

“…Concerning the definition of a membrane [47], which should be a medium that allows transfer to occur under a certain driving force, a TF [48] does not have such a restriction. The main difference between TFs and membranes lies in their functions, although there is reporting of freestanding MOF-TFs that can function as a membrane due to its porosity [49].…”