Pd Nanoparticles Supported on Amine-Functionalized MgAl Layered Double Hydroxides for Solvent-Free Aerobic Oxidation of Benzyl Alcohol

Pd nanoparticles (NPs) supported on amine-functionalized layered double hydroxides (LDHs) (Pd/NH2-LDH-NS) were successfully obtained by implanting aminopropyltriethoxysilane (APTS) on MgAl LDH nanosheets (LDH-NS), followed by impregnating [Pd(NH3)(4)]Cl-2 and reduction with NaBH4. The physicochemical characteristics of the obtained Pd/NH2-LDH-NS were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR),, N-2 adsorption-desorption, inductive coupled plasma (ICP), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS), and their catalytic performance was tested in the selective oxidation of benzyl alcohol with molecular oxygen under solvent-free and base-free conditions. The results showed that the implanted -NH2 groups can promote the dispersion of the supported Pd NPs via complexation of the implanted -NH2 groups to Pd NPs, and they can increase the surface basicity of the catalysts, thus enhancing the catalytic activity and selectivity to benzylaldehyde. Pd/NH2-LDH-NS exhibited enhanced catalytic activity (31.6%) and selectivity (>98%) compared to the corresponding Pd/LDH-NS, Pd/LDH, Pd/SiO2, and Pd/Al2O3. Moreover, Pd/NH2-LDH-NS was remarkably stable and could be reused at least four times without a significant loss in activity and selectivity.