Ultrasmall Au Nanoparticles Embedded in 2D Mixed-Ligand Metal-Organic Framework Nanosheets Exhibiting Highly Efficient and Size-Selective Catalysis

Metal-organic frameworks (MOFs) hold great promise as porous matrixes for the incorporation of Au nanoparticles (NPs) because of their rationally designed framework structures. Unfortunately, the as-synthesized bulk MOFs usually vary in the range of micrometer or sub-micrometer size, rendering extremely longer molecular diffusion distance of chemical species. 2D MOF nanosheets with extended lateral dimensions and nanometer thickness are expected to implement fast kinetics and effectively lower mass-transfer barriers during embedding Au NPs process and sequential catalytic reactions. In this study, a novel 2D nanosheet of mixed-ligand Ni(II) MOF (referred to NMOF-Ni) is successfully fabricated. With the merits of well-defined micropores and functional oxygen-decorated inner walls, the incorporation of quite monodisperse ultrasmall Au nanoparticles of around 1 nm into NMOF-Ni has been achieved for the first time. The resulting nanocomposites exhibit remarkable catalytic performance and good size selectivity toward aqueous reduction reactions of nitrophenol, taking advantage of ultrasmall Au and 2D nanosheet nature, as well as the intact microporosity of host matrix. The present encouraging findings might shed light on new ways to develop high-performance heterogeneous catalysts by using of 2D MOF nanosheets with functional cavities as hosts for homogeneous distribution of ultrasmall Au NPs.