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

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