(369b) Molecular Insight into Seawater Pervaporation through Zeolitic Imidazolate Framework Membranes
In this study, an atomistic simulation study is reported for seawater pervaporation through five zeolitic imidazolate framework (ZIF) membranes including ZIF-8, -93, -95, -97 and -100. Salt rejection in the five ZIFs is predicted to be 100% due to the sieving of small apertures. The hierarchy of water flux is as ZIF-100 >> -8 > -95 > -93 > -97. With the largest aperture, ZIF-100 possesses the highest water permeability of 5 ´ 10-4 kg×m/(m2×hr×bar), which is substantially higher compared to commercial reverse osmosis membranes, as well as zeolite and graphene oxide pervaporation membranes. In ZIF-8, -93, -95 and -97 with similar aperture size, water flux is governed by framework hydrophobicity/hydrophilicity; in hydrophobic ZIF-8 and -95, water flux is higher than in hydrophilic ZIF-93 and -97. Furthermore, water molecules in ZIF-93 move slowly and remain in the membrane for a long time, but undergo to-and-fro motion in ZIF-100. The lifetime of hydrogen bonds in ZIF-93 is found to be longer than in ZIF-100. This simulation study quantitatively elucidates the dynamic and structural properties of water in ZIFs, identifies the key governing factors and suggests ZIF-100 is an intriguing membrane for seawater pervaporation.