Investigating the structural relaxation of multivariate ZIF-76 derivatives during exothermic melting and glass formation by X-ray total scat

To date, only a little more than a handful of meltable zeolitic imidazolate frameworks (ZIFs) are known, all of them are rather dense frameworks of low porosity. The liquid state of highly porous ZIFs is usually inaccessible because their free energy barrier for melting is too high, so they decompose before melting. We now developed a strategy to facilitate the melting of the highly porous ZIF-76 by exchanging a fraction of its organic linkers against weaker binding ones. The derived multivariate ZIF-76 derivatives display strongly exothermic melting followed by glass formation upon cooling of the melt. The unprecedented exothermic melting transition of these ZIFs is grounded in the unusually high enthalpy and entropy of the multivariate crystalline phases compared to their liquids. Via X-ray total scattering experiments, we aim to derive structural details of the exothermic melting transitions, the liquid phase's relaxation processes and the corresponding glasses' structures.