Meltable, Glass-Forming,\nIron Zeolitic Imidazolate\nFrameworks

Abstract

We describe the first meltable iron-based zeolitic imidazolate\nframework (ZIF), denoted <b>MUV-24</b>. This material, elusive\nfrom direct synthesis, is obtained from the thermal treatment of [Fe₃(im)₆(Him)₂], which yields Fe(im)₂ upon loss of the neutral imidazole molecules. Different crystalline\nphase transformations are observed upon further heating, until the\nmaterial melts at 482 °C. Vitrification upon cooling of the liquid\nphase gives rise to the first Fe-metal–organic framework glass. X-ray total scattering experiments\nshow that the\ntetrahedral environment of the crystalline solids is maintained in\nthe glass, whereas nanoindentation measurements reveal an increase\nin Young’s modulus, in agreement with stiffening upon vitrification.