Hierarchical nanospheres based on Pd nanoparticles dispersed on carbon coated magnetite cores with a mesoporous ceria shell: a highly integrated multifunctional catalyst.

The design and fabrication of core-shell nanostructures with steerable morphologies and tailored performances have aroused abundant scientific studies for organic transformations. We here report the preparation of multifunctional and highly efficient core-shell microspheres, which bear a carbon-protected magnetic Fe3O4 core, a transition layer of active Pd nanoparticles (NPs) and an outer shell of mesoporous CeO2 (mCeO2). The composition and structure of the as-prepared Fe3O4@C-Pd@mCeO2 were thoroughly characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and Brunauer-Emmett-Teller measurements. The well-designed microspheres have high dispersibility, convenient magnetic separability and good reusability as heterogeneous nanoreactors due to their unique structure. We illustrate the high efficiency of these nanocomposites in mediating the Suzuki-Miyaura cross-coupling reaction and the reduction reaction of 4-nitrophenol (4-NP). The enhanced catalytic activity can be attributed to the synergistic effect between the CeO2 nanoparticles and noble metal NPs. A mechanism was further proposed to explain the improved catalytic activity. This peculiar core-shell nanostructure renders the nanospheres to be an approachable and attractive catalyst system for various catalytic organic industrial processes.