Selective Oxidation of Saturated Hydrocarbons Using Au-Pd Alloy Nanoparticles Supported on Metal-Organic Frameworks

Gold (Au) and palladium (Pd) nanoparticles dispersed on a zeolite-type metal-organic framework (i.e., MIL-101) were prepared via a simple colloidal method. The catalysts were characterized by powder X-ray diffraction, N-2 physical adsorption, atomic absorption spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Au and Pd were mostly in the form of bimetallic so alloys on the MIL-101 support. The Au-Pd/MIL-101 was active and selective in the oxidation of a variety of saturated (including primary, secondary, and tertiary) C-H bonds with molecular oxygen. For the liquid-phase oxidation of cyclohexane, cyclohexane conversion exceeding 40% was achieved (TOF: 19 000 h(-1)) with >80% selectivity to cyclohexanone and cyclohexanol under mild solvent free conditions. Moreover, the Au-Pd alloy catalyst exhibited higher reactivity than their pure metal counterparts and an Au + Pd physical mixture. The high activity and selectivity of Au-Pd/MIL-101 in cyclohexane aerobic oxidation may be correlated to the synergistic alloying effect of bimetallic Au-Pd nanoparticles.