Thin selective layered mixed matrix membranes (MMMs) with defective UiO-66 induced interface engineering toward highly enhanced pervaporation performance

The thin selective layer in mixed matrix membranes (MMMs) with high pervaporation performance is in high demand because of their high productivity. However, it has been limited because of the defective interface of sieving fillers in MMMs and the instability to permeate molecules, resulting in instability and degradation in the membrane state and pervaporation performance. Herein, we synthesized defective UiO-66 (DUiO66) by controlling the concentration of the reactants and then analyzed the characteristics of the defects. We confirmed that defects of the missing linker are induced in its structure, and DUiO66 (1.324) has a higher defect density than conventional UiO66 (1.064). Those led to the highly enhanced interface of DUiO66 with polyvinyl alcohol (PVA) matrix and water solvent, resulting in mechanical stability and a uniformed thin selective layer. Crosslinked thin-layered PVA MMMs with DUiO66 (XPDUiO66) were applied to the flat-sheet type and hollow fiber type membranes and then examined for the pervaporation performance to separate IPA/water solution (mainly 80/20 and 90/10 (w/w)). The thin-layered flat type and hollow fiber type XPDUiO66 revealed a dramatic increase in flux by 5.6 and 5.0 times compared to the free-standing type MMM while almost maintaining selectivity. Notably, the flat-sheet type XPDUiO66-2 increased around 606% and 1,664% in PSI relative to XPVA at a feed solution of 80/20 and 90/10 (w/w) IPA/water, respectively. The current work offers significant findings on the relationship between defective MOF-applied MMMs and pervaporation performance.