3.4 Thermal Analysis (TGA)
The thermal analysis of TG, DTA, and DTG is taken from a magnetic
metal-organic framework sample
NiFe2O4@SiO2@HKUST-1
with 30% (weight) and is shown in Fig. (7). Thermal analyses (TG, DTA,
DTG) are used to determine the thermal stability of the metal-organic
framework. As can be seen, two weight reductions are seen in the thermal
analysis of the graph (TG) and this is due to the synthesis process. The
first weight loss reported at 150-200 °C was related to the removal of
guest molecules (solvent: water and ethanol) inside the pores of the
metal-organic framework and gases adsorbed on the surface and partially
related to the decomposition of organic groups such as (Carboxyl groups,
etc.) on the surface of the magnetic nanocomposite, which is attributed
in the diagram (DTA) along with an exothermic peak in this range. The
second weight loss in the range of 300-400 °C is usually due to the
restructuring of the metal-organic framework, mostly related to the
metal oxides present in the metal-organic framework. It is reported that
severe weight loss at 350 °C signifies the collapse and complete
decomposition of the HKUST-1 metalorganic framework, and here the severe
weight loss at 355 °C occurs when the structure of the metal-organic
framework
NiFe2O4@SiO2@HKUST-1
begins breaks down. It can be concluded that the metal-organic framework
NiFe2O4@SiO2@HKUST-1 has
thermal stability at temperatures above about 350 °C.
Fig (7): thermal analysis of TG, DTA, and DTG for magnetic metal-organic
framework sample
NiFe2O4@SiO2@HKUST-1
with 30% (weight)
The peak in the DTA curve is reported the presence of sharp peaks in
region 300 and 400 °C indicates crystal deformation and the presence of
a broad peak in zone 200-70 °C due to chemical reactions as well as the
presence of a broad peak from 400 to 750 °C thermal decomposition. The
endothermic peaks can also be observed between 1100 and 750 °C due to
the compacting of the metal-organic composite because mass loss occurs
up to about 400 °C [54-56].