In the present study, a novel core–shell structured CoFe2O4/ MCM-41 composite was prepared through modification of MCM-41 nanoparticles with 3,4,5-tri hydroxyphenyl acetic acid (HA) followed by treatment with Mn (II) particles. The prepared material was denoted as CoFe2O4/ MCM-41/HA/Mn and characterized using high-resolution transmission electron microscopies (TEM), field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), vibratingsample magnetometer (VSM) and nitrogen adsorption−desorption isotherm. Results showed that the magnetite nanoparticles were coated with the MCM-41 silica with the formation of core–shell structured materials, and the 3,4,5-tri hydroxyphenyl acetic acid (HA) was successfully immobilized on the core–shell structured support. In this approach, the CoFe2O4/ MCM-41/HA/Mn composite with spherical particles consisted of mesoporous structure with a surface area by BET and t-plot of 189.9 m2 /g and 163.7 m2 /g respectively, mean pore size of 5.55 nm, and pore volume of 0.263 cm3 /g. The CoFe2O4/ MCM-41/HA/Mn was successfully applied as a powerful catalyst for green synthesis of 5-substituted 1H-tetrazoles in water and selective oxidation of sulfides at room temperature. This catalyst was recovered and reused several times without a significant decrease in efficiency and stability. CoFe2O4 can not only provide strong magnetization to the catalyst but also adjust its acidity to promote tetrazole production. The catalyst could be fully recovered by an external magnetic field and showed good reusability
