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 CO 2 . Most importantly, with increasing MOF loading, only the modified membranes exhibit simultaneous increase of selectivity and permeability for CO 2 /N 2 and CO 2 /CH 4 separation, following the trend predicted by the modified Maxwell model.

An ew strategy uses ac ommon feature of metalorganic frameworks (MOFs), namely porosity rather than functionality,t oa chieve simultaneous interior and exterior modification of aMOF with polymers.Wedemonstrate that an anhydride-terminated polyimide oligomer can be covalently grafted to the amine-functionalized methacrylate polymer backbone residing underneath the MOF surface and physically entangled within the 3D nanochannels.T he MOF particles were evenly coated with at hin layer of polyimide brushes on the surface thereby exhibiting increased dispersibility in solvent media as well as in polymer matrix. The MOF pores were decorated with aliphatic amine groups to endowthe MOF with higher CO 2 affinity at lowp ressure.T he polyimide-grafted surface allowed MOF particles to interact favorably with the polyimide matrix, producing defect-free MMM with drastically improved CO 2 permeability and maintaining the inherent CO 2 / N 2 and CO 2 /CH 4 selectivity of the neat polymeric membrane.

We report here a new technique for the identification and visualization of functional domains in stratified metal−organic frameworks (MOFs). The technique, namely, gold diffusion enabled domain identification, utilizes the diffusion of Au nanoparticles within MOF cavities to track and selectively stain the more Au-philic domain in an MOF particle thereby allowing direct observation of domains, determination of domain sequences, and, in certain cases, domain boundaries under transmission electron microscopy. This method is an excellent tool for studying MOF materials with complex domain hierarchy.