Encapsulating Pt Nanoparticles through Transforming Fe3O4 into MIL-100(Fe) for Well-Defined Fe3O4@Pt@MIL-100(Fe) Core–Shell Heterostructures with Promoting Catalytic Activity

Metal–organic framework (MOF)-based magnetic Pt catalyst Fe3O4@Pt@MIL-100(Fe) core–shell heterostructures were prepared through transforming Fe3O4 into MIL-100(Fe) in benzene-1,3,5-tricarboxylic acid solution along with encapsulating the Pt nanoparticles successively adsorbed onto the surface of the Fe3O4 nanosphere and the continuously forming surfaces of the growing MIL-100(Fe) crystals. This method circumvented the obstacles, controlling the formation of metal nanoparticles (MNPs) inside MOFs or regulating growth of MOFs around the MNPs, for preparing an MNP–MOF composite catalyst. The obtained well-defined Fe3O4@Pt@MIL-100(Fe) core–shell heterostructure was shown promoting catalytic activity on the reduction of 4-nitrophenol due to the synergistic effect between the Pt nanoparticles and the MIL-100(Fe) shell and recycling convenience due to the rapid separation of the Fe3O4 core under an external magnetic field.