Halogenated Metal-Organic Framework Glasses and Liquids

摘要

The synthesis of four novel crystalline zeolitic I imidazolate framework (ZIF) structures using a mixed-ligand approach is reported. The inclusion of both imidazolate and halogenated benzimidazolate-derived linkers leads to glass-forming behavior by all four structures. Melting temperatures are observed to depend on both electronic and steric effects. Solid-state NMR and terahertz (THz)/far-IR demonstrate the presence of a Zn—F bond for fluorinated ZIF glasses. In situ THz/far-IR spectroscopic techniques reveal the dynamic structural properties of crystal, glass, and liquid phases of the halogenated ZIFs, linking the melting behavior of ZIFs to the propensity of the ZnN_4 tetrahedra to undergo thermally induced deformation. The inclusion of halogenated ligands within metal—organic framework (MOF) glasses improves their gas-uptake properties.