Zinc Halide Flux-Assisted Vitrification of Metal–Organic Frameworks Enables Chemical Diversification and Tunable Gas Sorption

The vitrification of metal–organic frameworks (MOFs) enables melt processing into bulk, shaped and membrane-type porous materials, yet the limited chemical diversity of existing MOF glass formers restricts structural and functional tunability. Here, we demonstrate a general flux-melting strategy in which inorganic zinc halide glass formers (ZnCl 2, ZnBr 2 or ZnI 2 ) are co-melted with seven zeolitic imidazolate frameworks (ZIFs) spanning different imidazolate-type linkers and network topologies, including both established ZIF glass formers and frameworks that do not melt or vitrify on their own. The zinc halides act as compatible co-network formers and reactive fluxes, promoting extensive ligand exchange between halides and imidazolate linkers in the melt. This process generates mixed halide-imidazolate coordination glass networks whose structure, connectivity and porosity can be tuned systematically through composition. One of the resulting mixed coordination glasses displays substantially enhanced thermodynamic sorption selectivity for propylene over propane compared to its parent ZIF glass. These results establish zinc halide flux melting as a general route to expand the compositional space of MOF glasses and introduce mixed coordination networks as a new design paradigm for functional porous glasses.