Microwave-assisted synthesis of 2D Zr-MOF nanosheets supported gold nanocomposites as efficient catalysts for the reduction of 4-nitrophenol

Abstract

Two-dimensional metal-organic framework nanosheets (2D MONs) are excellent heterogeneous catalysts owing to their high density and accessible catalytic sites, reduced diffusion pathways for reactants/products, and fast electron transport. Moreover, the employment of 2D MONs as supports to encapsulate noble nanoparticles can not only stabilize the noble nanoparticles, but also significantly improve their catalytic activity through the synergetic effect between 2D MONs and noble nanoparticles. Herein, we reported a microwave-assisted method for the rapid preparation of 2D UiO-67 metal-organic framework nanosheets (named UiO-67 NS). The Au nanoparticles modified UiO-67 nanocomposites (denoted as Au/UiO-67 NS nanocomposites) are formed by the in situ reduction of HAuCl4 in the pores of UiO-67 NS. The Au/UiO-67 NS nanocomposites show excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol, and only 20 equivalent sodium borohydride can completely reduce 10 mM 4-NP in 100 s, thanks to highly exposed Au NPs and reduced diffusion distance. In addition, XPS characterizations showed that the binding energy of Au 4 f in Au/UiO-67 NS nanocomposites displays a 0.48 eV less than that of Au nanoparticles on UiO-67 octahedral microcrystals (denoted as Au@UiO-67 OM), which is believed to be responsible for the enhanced catalytic activity toward the reduction of 4-nitrophenol.