Polycrystalline zeolite and metal-organic framework membranes for molecular separations

Porous and crystalline materials such as zeolites and metal-organic frameworks (MOFs) have expanded the scope of membrane materials. In this review, we focus on the state-of-the-art polycrystalline membranes fabricated from these materials, as well as their crystalline structure, uniform microporosity and molecular-sieving capacity. We first discuss the basics of membrane-based separations and compare the transport properties between dense polymeric membranes and porous polycrystalline membranes. Subsequently, we evaluate the performance of polycrystalline zeolite/MOF membranes in applications such as gas separation, organic solvent nanofiltration, water purification, ion separation and chiral separation. Finally, we present a comparison between zeolite membranes and MOF membranes in terms of synthesis and chemical tunability. (C) 2021 Elsevier B.V. All rights reserved.