Achieving a balance between permeability and selectivity in a ZIF-8-matrix nanocomposite membrane for desalination

Abstract

Hybrid metal–organic framework (MOF)-polymer membranes are promising for addressing the permeability-selectivity tradeoff in membrane applications. The key challenges for achieving high-efficiency separation performance have been identified as increasing the MOF loading while maintaining interfacial compatibility with polymeric matrices. Herein, a novel design of ZIF-8 matrix nanocomposite membrane, with ZIF-8 nanoparticles (NPs) serving as the main matrix, was prepared by functionalizing the external surface of zeolitic imidazolate framework-8 (ZIF-8) NPs with polyethyleneimine and subsequent crosslinking into the selective layer using trimesoyl chloride as a crosslinking agent via confined interfacial polymerization. The content of ZIF-8 NPs in the selective layer was up to about 70 wt%, resulting in superior permeability (＞ 43.6 LMH bar−1) for desalination due to the large number of transport channels, which was several folds as compared to most of the reported membranes. Meanwhile, a reasonably high Na2SO4 rejection (∼95.1 %) was maintained as the polyamide fragments formed during interfacial polymerization, which filled defects among the ZIF-8 NPs. Overall, such strategy paves the way for the design of efficient MOF-based membranes for balancing between permeability and selectivity in desalination.