Interfacial Engineering in Metal–Organic Framework-Based Mixed Matrix Membranes Using Covalently Grafted Polyimide Brushes

Abstract

Good interfacial compatibility is the key to realize the full potential of metal-organic framework-based mix matrix membranes for gas separation. Here we report a new approach that uses polyimide brushes covalently grafted on the MOF surface to engineer the MOF-polymer interface. Benefiting from the strong brush-brush interaction, polyimide grafted MOF particles can form a stand-alone membrane at 88 wt % MOF loading without the addition of polymeric matrix. Compared to traditional mixed-matrix membranes, the modified membranes exhibit improved ductility up to 472%, reduced interfacial tearing phenomenon under shear force, decreased matrix chain mobility, and improved plasticization resistance against CO₂. Most importantly, with increasing MOF loading, only the modified membranes exhibit simultaneous increase of selectivity and permeability for CO₂/N₂ and CO₂/CH₄ separation, following the trend predicted by the modified Maxwell model.