Thermal Decomposition and Kinetic Analysis of a Mil-88a Metal-organic Framework

Abstract

The thermal decomposition of the MIL-88A metal-organic frameworks (MOFs) is studied, for the first time, at various heating rates under air and Nitrogen. The precursors of a MIL-88A material revealed water evaporation and remaining solvent molecules in the framework structure at low-temperatures range while at the high-temperatures range, the organic skeleton collapse; in the meantime, Fe0.94O and the shell of graphitized carbon are formed. Thermogravimetric analysis (TGA) curves of MIL-88A moved slowly to the high-temperatures region with increasing heating rates. Additionally, Differential Scanning Calorimetry (DSC) curves of MIL-88A provided a change in the peak intensity, indicating the difference in the sample weight loss. X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) of the as-prepared sample confirmed the existence of a single hexagonal MIL-88A without any impurities of other phases. However, XRD exhibited two phases Fe0.94O and F0, after annealing. TEM of the annealed sample also asserted the creation of a carbon layer on the surface. The activation energy and kinetic parameter of the MIL-88A material offered higher values as the exothermic peak increased. Interestingly, the thermal decomposition of the MIL-88A material is effective in investigating the temperature effect on the pyrolysis process that can benefit in energy storage applications.