Magnetic Fe3O4@MIL-100(Fe) core-shells decorated with gold nanoparticles for enhanced catalytic reduction of 4-nitrophenol and degradation of azo dye

Abstract

In this contribution, the metal-organic framework Fe3O4@MIL-100(Fe) have been successfully synthesized via in situ single-step hydrothermal route, where Fe3O4 not only acts as a core but also provide Fe(III) for uniform growth of MIL-100(Fe) shell around Fe3O4 microspheres. Compared with Fe3O4, both surface area and pore volume of Fe3O4@MIL-100(Fe) is significantly enhanced while the magnetism is slightly affected. The synthesis procedure is facile since it eliminates the need of the functionalization of Fe3O4 core with mercaptoacetic acid (MAA), addition of external iron source and repeated cycles of growth and washing. The as-prepared MIL-100(Fe) were decorated with gold nanoparticles (Au NPs) by deposition-reduction method for the first time and applied for fast detection and reduction of 4-Nitrophenol (4-NP) and azo dye to reduce their environmental and health issues. With N2 physisorption, XRD, TEM, SEM, VSM and FT-IR characterization, the metallic Au NPs were identified to be highly dispersed in the Fe3O4@MIL-100(Fe) cages without affecting the magnetism. For Au/Fe3O4@MIL-100(Fe), complete reduction of 4-NP and azo dye occurred within 16 min with reaction rate constant (k) of 0.25 and 0.2 min−1, respectively superior to Fe3O4 core and Fe3O4@MIL-100(Fe), which is attributed to well dispersive Au NPs, texture, and core shell surface of Fe3O4@MIL-100(Fe). Furthermore, the excellent reusability of Au/Fe3O4@MIL-100(Fe) makes it attractive to be used for multiples cycles in catalysis.