Fabrication of Fe3O4/PAH/PSS@Pd core–shell microspheres by layer-by-layer assembly and application in catalysis

•A novel Fe3O4/PAH/PSS@Pd magnetic core–shell microsphere catalyst material has been successful fabricated.•The resulting microspheres can be easily separated under magnetic field.•Excellent structural uniformity and superior catalytic activity for oxidation of benzyl alcohol. High performance magnetic Fe3O4/PAH/PSS@Pd core–shell microspheres are successfully synthesized via layer-by-layer self-assembly method. Fe3O4 cores with a rough surface are synthesized by hydrothermal method. Subsequently, Pd nanoparticle shells and Fe3O4/PAH/PSS@Pd microspheres are in situ simultaneously constructed by alternating immersion of Fe3O4 particles in PSS (poly(sodium 4-styrenesulfonate)) and PAH-Pd(II) (Poly(allylamine hydrochloride)-Pd(II)) solutions, followed by chemical reduction in NaBH4 solution. The structural and magnetic properties of microspheres are characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and vibrating sample magnetometer (VSM), respectively. These microspheres demonstrate excellent structural uniformity (190nm) and superior magnetization, leading to easy collection of microspheres using an external field. With highly active and stable Pd nanoparticle shells, these microspheres exhibit more efficient catalytic activity for the oxidation of benzyl alcohol.