Thermally Induced Disordering and Crystallization of DUT-67

Metal-organic frameworks (MOFs) are often considered purely crystalline materials. Zirconium based MOFs are different, as they require multiple specific solvents to guide the crystallization process. Without these solvents the frameworks become inherently disordered. DUT-67 is a zirconium MOF that owes its specific crystal structure to the addition of acetic acid during the solvothermal synthesis, which results in crystalline material with greater porosity than its polymorphs. This also leads to an inherently unstable crystal structure, which is prone to disordering upon heating. DUT-67 showcases anomalous behavior which results in disordering and rearrangement of the structure into DUT-67 HT. To understand the behavior and the properties of the disordered state, characterization with differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FT-IR), gas sorption, in-situ x-ray diffraction, and in-situ small angle x-ray scattering (SAXS) were performed.