Fabrication of Integrated Cu2O@HKUST-1@Au Nanocatalysts via Galvanic Replacements toward Alcohols Oxidation Application

Metastable Cu 2 O is an attractive material for the architectural design of integrated nanomaterials. In this context, the in situ growth of microporous metal–organic frameworks (MOFs) on Cu 2 O nanocrystals with well-defined shapes (such as octahedron, truncated octahedron, and corner-truncated cube) was conducted under ambient conditions by using sacrificial Cu 2 O nanocrystals as a copper ion source for the construction of HKUST-1. It was found that the growth rate of HKUST-1 on the (111) facet of octahedral Cu 2 O was much faster than that on the (100) facet of cubic Cu 2 O. A subsequent etching process on the core–shell-structured Cu 2 O@HKUST-1 to remove Cu 2 O results in hollow HKUST-1 with hierarchical pores, where the shapes of cavities are tailored depending on the original Cu 2 O crystals. Importantly, it was found that the integrated Cu 2 O@HKUST-1@Au nanocatalysts could be fabricated by galvanic replacement reaction between Cu 2 O and AuCl 4 –, wherein the copper(I) ions from Cu 2 O etching diffuse through the microporous MOF shell and reach to the external surface to reduce AuCl 4 – ions, thereby forming Au nanoparticles exclusively on the MOF external surface. Furthermore, the catalytic applications of Cu 2 O@HKUST-1@Au toward liquid-phase oxidation of both aromatic and aliphatic alcohols were studied. Notably, 100% selectivities of aldehyde products were achieved without any further oxidation byproducts such as acid and ester.