Interfacial polymerization of MOF “monomers” to fabricate flexible and thin membranes for molecular separation with ultrafast water transport

Abstract

Metal–organic framework (MOF) membranes with sub-nanometer channels have great potential in molecule selective transport, but the scalable and facile fabrication of flexible and thin membranes from stable MOF structures is difficult, which is the key to realizing practical applications. In this work, stable and ultra-small MOF nanoparticles act as “ordered porous monomers” and are interfacially polymerized with organic monomers into ultra-thin and flexible membranes. An ∼150 nm thin MOF active layer can be produced rapidly (<10 minutes) and economically (∼30 USD m⁻²) on a commercial polymer substrate. With their uniform pore size and thin membrane thickness, the membranes possess a long-lasting dye rejection rate (99.8%) and high water permeance (up to 55.9 L m⁻² h⁻¹ bar⁻¹), which is 30 times higher than that of commercial DK nanofiltration membranes. Remarkably, the scalable and stable membrane can maintain the superior separation performance after being rolled up 20 times with a curvature of 200 m⁻¹, suggesting that the flexible membrane could be used to construct a spiral wound membrane module. The strategy adopted here has been extended to other crystalline porous materials such as metal–organic cages for flexible and thin membrane fabrication.