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.