3.1 Characterization of synthesized magnetic metal-organic framework nanocomposite
The synthesized magnetic metal-organic framework nanocomposite with different weight ratios from ferrite nickel and silica substrate was characterized by analyzes SEM, TEM, XRD, VSM and BET.
Fig (1): TEM analysis image of magnetic metal-organic framework nanocomposite (NiFe2O4@SiO2@HKUST-1)
Fig 1 shows the image of the electron microscopy associated with the magnetic metal-organic framework nanocomposite (NiFe2O4@SiO2@HKUST-1) synthesized in this study with magnification KX200. According to the image, the metal-organic framework nanocomposite were almost rod-shaped, and the nickel ferrite were dispersed inside and outside the silica substrate. In this study, to analyze the morphology and size of the magnetic metal-organic framework nanocomposite (NiFe2O4@SiO2@HKUST-1), the analysis of scanning electron microscopy were used.
Fig. (2): Image analysis of SEM analysis of magnetic metal-organic framework nanocomposite NiFe2O4@SiO2@HKUST-1
SEM of the synthesized magnetic metal-organic framework shows that these nanocomposites have rod morphology (Fig.2). The nickel ferrite nanoparticles in the silica matrix are placed side by side in such a way that they form a rod structure and the HKUST-1 metal-organic framework is placed on them. It has also been shown that the synthesized nanocomposite is hollow and has a crystalline and dense structure [46].
The X-ray diffraction analysis was used to investigate the formed phases and the structure of the synthesized magnetic metal-organic framework nanocomposites and to calculate the size of the crystals. Fig (3) shows the XRD diagram of the synthesized samples.
Fig (3): XRD diagram of magnetic metal-organic framework nanocomposite synthesized with different nickel ferrite percentages
The crystal structure of metal-organic framework (HKUST-1) at 2θ has index peaks at 20.66°, 15.92° and 13.65°, as well as the presence of index peaks at 20-35° related to nickel ferrite and the presence of silica in the nanocomposite. Peaks at the 52- 40 degree range are due to the presence of nickel ferrite in the silica substrate, indicating that the xerogel amorphous nickel ferrite is located in the silica matrix. Finally, the Sherler equation was used to calculate the crystal size of the synthesized magnetic metal-organic framework. Crystal sizes obtained from Equation (8) showed that the higher ratio of nickel ferrite to the silica matrix led to the larger nanocomposite. In Table 2, the crystal sizes for synthesized magnetic metal-organic framework nanocomposites are calculated and presented.
D = 0.99λ / β cos θ (8) Eq.
In this regard, D diameters of nanocomposites, λ is the X-ray wavelength irradiated, β is the peak width at half height or FWHM, which should be placed in the formula according to radians and θ is the peak location on the horizontal axis of the scatter pattern.
Table (2): Crystal parameters of synthesized magnetic metal-organic framework nanocomposites