Enhanced metal-support interactions between Pd NPs and ZrSBA-15 for efficient aerobic benzyl alcohol oxidation

Towards the aerobic oxidation of alcohols, palladium nanoparticle immobilized mesoporous catalysts have been extensively investigated; however, the preparation of efficient catalytic materials without using complexing moieties remains a challenge. Herein, a simple yet effective concept that directly utilizes inorganic ZrSBA-15, a mild acidic framework, as a supporting matrix for Pd NPs was applied. The catalysts were fully characterized using X-ray diffraction, N-2 adsorption-desorption isotherms, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. It was demonstrated that, on the basis of these characterization results, active Pd NPs had been successfully loaded onto the porous framework of ordered ZrSBA-15. More significantly, the method of preparation was also attributed to the catalytic properties of the resultant sample, in which the interactions between Pd species and acidic framework were improved, leading to a uniform dispersion and enhanced stabilization of Pd particles. Meanwhile, Pd/ZrSBA-15 catalysts exhibited expected activity in the aerobic oxidation of benzyl alcohol with at least 95% conversion and 99% selectivity for benzaldehyde. Moreover, the oxidation reaction could be performed smoothly under solvent-and base-free conditions, and the catalyst was recycled several times with negligible loss in selectivity and conversion.