Facile synthetic route of TiO2-ZnO heteronanostructure coated by oxovanadium (IV) bis-Schiff base complex as a potential effective homogeneous/heterogeneous catalysts for alcohols redox systems

Oxovanadium (IV) bis-Schiff base complex was synthesized by a facile complexation of 2 molar ratio of 2-hy-droxy-Schiff base ligand (HL) with 1 molar ratio of VO2+ ion giving mononuclear VOL2 complex with a square pyramidal geometry. The structure conformation of HL and its corresponding VOL2 complex was assigned within various spectroscopic tools (IR, UV-vis. Mass spectra), as well as the elemental analyses (EA). The deprotonated 4-OH group in VOL2 caused a successful coating of VOL2 on a mixed oxides of TiO2-ZnO nanoparticles awarding nanocomposite of TiO2-ZnO@VOL2. By applying alternative analytical techniques, the surface morphology and internal structure TiO2-ZnO@VOL2 nanocomposites were investigated compared to that of TiO2-ZnO, i.e. by XRD, FESEM, HR-TEM, EDS and IR spectra), and also with TGA and BET (adsorption-desorption isotherm).The catalytic effectiveness of both homogeneous and heterogeneous catalysts (VOL2 and TiO2-ZnO@VOL2) was examined in the productive oxygenation reactions of BA (benzyl alcohol) by an aqueous hydrogen peroxide under an aerobic environment to the chemo-selective product benzaldehyde (BZ), and benzoic acid (BO), as the overodixation product. Both VOL2 and TiO2-ZnO@VOL2 catalysts exhibited obvious classified action by 89% and 91% yielding amount of benzaldehyde after 4 h for reaction temperature 80 and 90 degrees C, respectively. The dif-ferentiation between them in the catalytic reactivity was depending on the heterogeneity and the effect of the coated TiO2-ZnO nanoparticles on the VOL2 catalytic potential. The kinetic parameter of the productive redox protocols for both catalyst was examined. Additionally, some other cyclic and acyclic alcohols were exhibited the productive redox protocol in the optimum control of both catalysts.

Automated summary

Oxovanadium (IV) bis-Schiff base complex was synthesized through a simple complexation between 2-hydroxy-Schiff base ligand (HL) and VO2+ ion, resulting in a mononuclear VOL2 complex with a square pyramidal geometry. The structure of HL and VOL2 complex was determined using spectroscopic techniques and elemental analysis. The VOL2 complex was successfully coated on TiO2-ZnO nanoparticles, forming a nanocomposite of TiO2-ZnO@VOL2. The surface morphology and internal structure of TiO2-ZnO@VOL2 nanocomposites were studied using various characterization techniques. The catalytic effectiveness of VOL2 and TiO2-ZnO@VOL2 catalysts was evaluated in the oxygenation reactions of benzyl alcohol, where both catalysts exhibited significant catalytic activity. The difference in catalytic reactivity was attributed to the heterogeneity and the effect of coated TiO2-ZnO nanoparticles on the VOL2 catalytic potential. The kinetic parameters of the redox protocols for both catalysts were determined, and the catalytic system was found to be effective for other alcohols as well.