Mixed matrix membranes with nano-sized functional UiO-66-type MOFs embedded in 6FDA-HAB/DABA polyimide for dehydration of C1-C3 alcohols via pervaporation

This study demonstrated an effective method to enhance both the normalized flux and separation factor by molecularly designing mixed matrix membranes (MMMs) consisting of porous UiO-66-NH2 nanoparticles and 6FDA-HAB/DABA polyimide. To investigate the effects of functional groups on UiO-66 particles on alcohol dehydration, MMMs containing (1) UiO-66-NH2 nanoparticles with a particle size of 80-90 nm, (2) UiO-66 with a particle size of 90-110 nm and (3) UiO-66-F-4 with a particle size of 90-130 nm were fabricated and compared for alcohol dehydration. Three alcohol dehydration systems; namely, methanol/water, ethanol/water and isopropanol/water were studied. Results showed that UiO-66-NH2 based MMMs have superior separation performance among these three MMMs because the hydrophilic amino-functional groups can facilitate water transport. Incorporation of UiO-66-NH2 nanoparticles can greatly improve both the normalized flux and separation factor simultaneously if the particle loading is within the range of 0-20 wt%. Due to the good compatibility between UiO-66-NH2 particles and the 6FDA-HAB/DABA polyimide resulting from the intermolecular bonding among the amine and imide groups, the UiO-66-NH2 based MMMs exhibited stable isopropanol dehydration performance in uninterrupted 200-h tests. The excellent alcohol dehydration performance of UiO-66-NH2 based MMMs opens up their potential for alcohol dehydration via pervaporation.