NiFe2O4@SiO2@Cu3(BTC)2 nanocomposite as a magnetic metal–organic framework

Abstract

A new magnetic metal–organic framework (MOF), namely, NiFe2O4@SiO2@Cu3(BTC)2, was synthesized via an in situ method using Fe(NO3)3, Ni(NO3)2, CuN2O6, TEOS, (3‐aminopropyl)triethoxysilane, and benzene‐1,3,5‐tricarboxylic acid. Three different samples were fabricated according to a formula; xNiFe2O4@(100 − x)SiO2@Cu3(BTC)2, where x = 10, 30, and 50. The integration of the intrinsic characteristic of Cu3(BTC)2 as an MOF with strong magnetic properties of NiFe2O4 could lead to an exquisite material with specific behaviors. X‐ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and simulated thermal analyzer (STA) were utilized to characterize the mentioned samples. Results approved that the synthesized compounds were composed of SiO2 and Cu‐MOF and NiFe2O4 crystalline phases with rod‐like morphology. The similarity between the morphology of the synthesized samples and Cu‐MOF approved that an appropriate fabrication method has been selected. This fact led to observe mesoporous composites with 38–90 m2 g−1 specific surface area. PL spectroscopy confirmed the near bandgap emission, ligand‐to‐metal charge transfer, and metal‐to‐ligand charge transfer. Although all the samples had magnetic hysteresis, the highest magnetization was seen in the 50NiFe2O4@SiO2@Cu3(BTC)2 sample. This composite compound with a magnetization value of 2 emu g−1 at 8000 Oe and a specific surface area of 90 m2 g−1 could be classified as a magnetic MOF (MMOF). STA results suggested that 400°C is the highest operating temperature for this compound.