Covalent cross-linking for interface engineering of high flux UiO-66-TMS/PDMS pervaporation membranes

Abstract

Interface compatibility between hydrophilic metal-organic frameworks (MOFs) and hydrophobic polydimethylsiloxane (PDMS) is less effectively reconciled through supramolecular modifications such as surfactant and polymer wrapping. Here we report a covalent cross-linking strategy to strengthen MOFs ~ PDMS interfaces. Zirconium MOFs (UiO-66-NH2) were modified with trimethoxysilan (TMS), which could further react with silanol terminated PDMS to enhance UiO-66 ~ PDMS interface compatibility. High content UiO-66-TMS (up to 50 wt%) were loaded into PDMS while retaining good membrane formation ability, mechanical properties and pervaporation selectivity, in contrast to pristine UiO-66-NH2 that decreases membrane strength and separation performances even at much lower loading content (10 wt%). Flux of mixed matrix membranes in dehydrating ethanol-water mixtures was highly improved while retaining the selectivity. It allows for the efficient production of concentrated ethanol (equivalent flux: 2234 g/m2h; ethanol in permeate: 53 wt%) from dilute feed through two-times consecutive pervaporation at 40 °C. Moreover, the membrane with covalently enhanced interfaces exhibit stable performance during 100 h continuous operation.