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Facile hydrogen-bond-assisted polymerization and immobilization method to synthesize hierarchical Fe3O4@poly(4-vinylpyridine-co-divinylbenzene)@Au nanostructures and their catalytic applications.

Hierarchical Fe3O4@poly(4-vinylpyridine-co-divinylbenzene)@Au (Fe3O4@P(4-VP-DVB)@Au) nanostructures were fabricated successfully by means of a facile two-step synthesis process. In this study, well-defined core-shell Fe3O4@P(4-VP-DVB) microspheres were first prepared with a simple polymerization method, in which 4-VP was easily polymerized on the surface of Fe3O4 nanoparticles by means of strong hydrogen-bond interactions between -COOH groups on poly(acrylic acid)-modified Fe3O4 nanoparticles and a 4-VP monomer. HAuCl4 was adsorbed on the chains of a P(4-VP) shell and then reduced to Au nanoparticles by NaBH4, which were embedded into the P(4-VP) shell of the composite microspheres to finally form the Fe3O4@P(4-VP-DVB)@Au nanostructures. The obtained Fe3O4@P(4-VP-DVB)@Au catalysts with different Au loadings were applied in the reduction of 4-nitrophenol (4-NP) and exhibited excellent catalytic activity (up to 3025 h(-1) of turnover frequency), facile magnetic separation (up to 31.9 emu g(-1) of specific saturation magnetization), and good durability (over 98 % of conversion of 4-NP after ten runs of recyclable catalysis and almost negligible leaching of Au).