General and Facile Method to Fabricate Yolk-like Structural Magnetic Nanocatalysts

A general and facile method for synthesis of yolk-like nanocomposite composed of superparamagnetic core and mesoporous SiO2 (mSiO2) shell with functional nanoparticles (Pd, Au, Pt) uniformly dispersing on their inner wall is reported. First, the magnetic particle (MP) was modified with resorcinol/formaldehyde resin (RF) layer. Then, the obtained MP@RF core–shell particle was decorated with functional metal nanoparticles such as Pd, Au, or Pt (defined as MP@RF-Pd, MP@RF-Au and MP@RF-Pt, respectively). To protect the metal nanoparticles, another hybrid CTAB/SiO2 (hSiO2) shell was constructed on the above particle through the surfactant-templated sol–gel process. After calcination, the yolk-like nanocomposites such as MP@Void-Pd@mSiO2, MP@Void-Au@mSiO2, and MP@Void-Pt@mSiO2 were successfully obtained. Because of the unique yolk-like structure, the as-prepared nanomaterials can be served as ideal nanoreactors for heterogeneous catalysis. The Heck reaction and the reduction of p-nitrophenol (4-NP) were introduced as model reactions to evaluate the catalytic activities of the magnetic nanocatalysts. Benefitted from the high dispersity of noble metals, large specific surface area and the mSiO2 protective shell, all samples exhibited remarkable catalytic activity and reusability. After 7 cycles, the activities of MP@Void-Pd@mSiO2 and MP@Void-Au@mSiO2 could maintain as high as 98% and 81%, respectively.