The magnetic nanocomposites [magnetite@silica@titania@metallomeso-tetra(hydroxyphenyl)porphyrin, Fe3O4@SiO2@TiO2@MTHPP] (MSiTMP; M = CoIII, ZnII, NiII) and [Fe3O4@SiO2@TiO2] (MSiT) have been synthesized and characterized. These nanocomposites were used to degrade of methylene blue (MB) under the blue light-emitting diode (LED) lamp irradiation. The degradation of MB was monitored by UV-Vis spectrometry. Upon a 180 min irradiation period maximum degradation of MB in presence of MSiTNiIIP, MSiTZnIIP, MSiTCoIIIP and MSiT photocatalysts were 90, 80, 63 and 48% g-1, respectively. After three 180 min runs, the photocatalysts still exhibited good activity. From Ultra-Violent-Diffuse reflectance spectroscopy spectra, the band gap energies of the photocatalysts were found to be 2.6, 2.5, 2.4 and 2.2 eV for MSiT, MSiTCoIIIP, MSiTZnIIP and MSiTNiIIP, respectively. The results consist with the observed relative photocatalytic activity of the photocatalysts which is as follows: MSiTNiIIP > MSiTZnIIP > MSiTCoIIIP > MSiT. The higher photocatalytic properties of MSiTNiIIP photocatalyst may be due to the fact that it is more susceptible to receive electron and reach to steady state than that of ZnII and CoIII complexes. The degradation of MB using these nanocomposites were found to follow the pseudo first order kinetics.
