Hibiscus rosa-sinensis Leaf Extracted Green Methods, Magneto-Optical and Catalytic Properties of Spinel CuFe2O4 Nano- and Microstructures

Spinel CuFe2O4 nano- and microstructures were synthesized by a simple, economical and eco-friendly microwave heating (MHM) and modified sol-gel methods (SGM) using metal nitrates and Hibiscus rosa-sinensis leaf extracted solution, instead of toxic inorganic/organic catalyst, template and surfactant. Powder XRD, FT-IR, EDX and SAED results were confirmed that the as-synthesized products have a single-phase spinel structure with high crystallinity and without the presence of any other secondary phase impurities. The morphology of the samples was revealed by HR-SEM and HR-TEM techniques show that the MHM and SGM products consist of nano- and microstructures, respectively, and their possible formation mechanisms were also proposed. The optical band gap (E (g) ) was measured using Kubelka-Munk model and it shows higher value (2.35 eV) for CuFe2O4-MHM than CuFe2O4-SGM (2.18 eV), due to the smaller particle size of CuFe2O4-MHM. The magnetic property of the samples showed a ferromagnetic behavior and the magnetization (M-s) value of CuFe2O4-MHM is higher i.e. 61.13 emu/g than CuFe2O4-SGM (57.25 emu/g). Both the samples were successfully tested as catalysts for the conversion of benzylic alcohols to respective carbonyls using H2O2 (as oxidant) and acetonitrile (as a solvent) catalytic system. It was found that the CuFe2O4-MHM catalyst show best performance of conversion of aromatic alcohols into aldehydes than that of CuFe2O4-SGM. Spinel CuFe2O4 catalyst is magnetically recyclable and could be reused with no significant loss in catalytic activity as proved for five consecutive cycles.