| dc.description.abstract | This study consists of two main parts. In the first part, the Palladium nanoparticles (Pd NPs) with a particle size of 2-3nm are successfully confined within the 2D mesoporous silica SBA-15 and the 3D mesoporous silica KIT-6. Under the wet impregnation process, SBA-15 and KIT-6 were immersed in Pd2+ precursor and adsorbed into the pores, then. The mixture chemically reduced by reagent containing NaBH4 and NH3BH3 to obtain Pd(x)@SBA-15 and Pd(x)@KIT-6. It was found that the use of SBA-15 and KIT-6 support can highly enhance the dispersion and efficiency due to the high surface area and large pore volume. In addition, SBA-15 and KIT-6 with the pore size of 9.09 nm and 9.56 nm, respectively, may effectively confine the Pd NPs and subsequently avoid the aggregation. According to the X-ray diffraction pattern and TEM image, it can be confirmed that the particle size of Pd NPs is about 2-3 nm and highly dispersed without aggregation. The Pd(x)@SBA-15 and Pd(x)@KIT-6 exhibited superior catalytic activity and chemoselectivity for the catalytic transfer hydrogenation of styrene under mild conditions with formic acid and ammonium formate as a hydrogen donor. Among all the as-prepared catalysts, the Pd(30)@KIT-6 exhibited the highest turnover frequency (TOF) of 363 h-1. In addition, Pd(30)@KIT-6 exhibited an excellent high stability after five successive cycles without significant loss of its catalytic activity.
In the second part of study, heteroatom doped carbon materials have received considerable attention in the field of catalysis. Herein, we report a catalyst made of palladium nanoparticles (Pd NPs) supported on mesoporous nitrogen-doped carbon (MUFC), Pd@MUFC. The use of the mixture of melamine-urea-formaldehyde as a precursor and the mesoporous silica SBA-15 as a hard template afforded a high-nitrogen-content mesoporous carbon material that showed high activity in stabilizing Pd NPs. The N-doped mesoporous carbon, MUFC, can provide a large surface area to adsorb the reductant and substrate, and enhance the accessibility of the active sites of the Pd NPs in the catalytic reaction process. When Pd@MUFC was applied as catalyst in the catalytic aerobic oxidation of benzyl alcohol, it achieved conversion rate and selectivity of 99.9% within 30 minutes. Among all the as-prepared catalysts, the Pd(30)@MUFC exhibited the highest turnover frequency of 750 h-1. The remarkable catalytic activity for the benzyl alcohol oxidation can be attributed to the ultra-small Pd NPs confined in the hexagonal N-doped carbonaceous MUFC. | en_US |