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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.

Zero valent iron (ZVI) is recently regarded as a promising alternative for water disinfection, but still suffers from low efficiency. Herein we demonstrate that amorphous zerovalent iron microspheres (A-mZVI) exhibit both higher inactivation rate and physical removal efficiency for the disinfection of Escherichia coli than conventional crystalline nanoscale ZVI (C-nZVI) under aerobic condition. The enhanced E. coli inactivation performance of A-mZVI was mainly attributed to more reactive oxygen species (ROSs), especially free •OH, generated by the accelerated iron dissolution and molecular oxygen activation in bulk solution. In contrast, C-nZVI preferred to produce surface bound •OH, and its bactericidal ability was thus hampered by the limited physical contact between C-nZVI and E. coli. More importantly, hydrolysis of dissolved iron released from A-mZVI produced plenty of loose FeOOH to wrap E. coli, increasing the dysfunction of E. coli membrane. Meanwhile, this hydrolysis process lowered the stability of E. coli colloid and caused its rapid coagulation and sedimentation, favoring its physical removal. These findings clarify the indispensable roles of ROSs and iron corrosion products during the ZVI disinfection, and also provide a promising disinfection material for water treatment.

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