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In this work, a series of Pd@Al-MSiO2 yolk–shell-structured nanospheres (YSNSs) with different Al contents were synthesized by a facile one-pot method. The EDX elemental analysis and high-magnification TEM image of Pd@Al-MSiO2 YSNSs confirmed that its well-defined yolk-shell structure with a moving Pd core and mesoporous silica shell rich in Al species. Furthermore, Solid state NMR and Py-FTIR results confirmed that Al species grafting mainly formed 4-coordinated Al (AlO4) in the mesoporous silica framework which led to generating abundant Lewis acid sites. The influence of Al species on the physicochemical properties of Pd@Al-MSiO2 YSNSs, as well as their catalytic performance for the hydrogenolysis of glucose to 1,2-propylene glycol (1,2-PG), was investigated. The mesoporous silica shell with abundant Lewis acid sites is a significant contributor to the isomerization of glucose into fructose, while the Pd core plays a role in promoting the hydrogenation of intermediates. The unique hollow space inside the Pd@Al-MSiO2 YSNSs provides a location for the retro-aldol condensation of fructose and consequently avoids direct hydrogenation of fructose. The as-synthesized Pd@Al3-MSiO2 YSNSs shows superior catalytic activity (1,2-PG selectivity of 47.4%, glucose conversion of 95.4%) in the hydrogenolysis of glucose, and far outperforms the Pd/Al3-MSiO2 catalysts. In addition, owing to the influence of the 4-coordinated Al species on the geometry and chemical properties of the mesoporous silica shell, the nanospheres show good stability and reusability over multiple catalytic cycles without significant loss of activity.

A supported ruthenium (Ru) nanoparticle on amino-functionalized Fe3O4 (Fe3O4/NH2/Ru) was successfully prepared by a novel and simple one-pot template-free method combined with a metal adsorption-reduction procedure. The characterization results show that the introduced amino group (1,6-hexanediamine) can effectively stabilize the Ru nanoparticles and allow the particles to maintain a narrow size distribution, monodispersity and a regular morphology. Fe3O4/NH2/Ru exhibits excellent catalytic activity for the transfer hydrogenation of nitro compounds by the use of NaBH4 as the hydrogen donor. The higher activity of this catalyst was attributed to the higher dispersion and smaller particle size of Ru nanoparticles, as observed from the characterization results. Moreover, the catalyst can be easily recovered by an external magnetic field, recycled five times and reused without any loss of activity.