Catalytic Nano-Gold Immobilized on the Inner Surfaces of Halloysite Nanotubes for Selective Reduction of Nitroaromatics

In catalytic reactions, the diverse binding sites of nanometals located in nanomaterials considerably influence the activity of nanocatalysts. In this study, the special nanostructure and charge distribution of halloysite nanotubes (HNTs) incorporating a weak reducing agent closo-dodecaborate (closo-[B12H12]2–) were leveraged to immobilize Au nanoparticles (NPs) on the inner and outer surfaces of HNTs. The introduction of closo-[B12H12]2– into HNTs was achieved via vacuum extraction and acid immersion. Subsequently, nanocatalysts loaded with Au NPs on the diverse surfaces of the HNTs were obtained from a direct reaction with a KAuCl4 solution. The Au NPs loaded on the inner surface of the HNTs were found to have highly dispersed and exhibited excellent catalytic activity in the reduction of nitroaromatics. At room temperature, the Au NPs loaded on the inner surface of the HNTs with a mass fraction of 0.02% showed a high turnover frequency value of 47.28 min–1 in a model reaction of the catalytic reduction of 4-nitrophenol to 4-aminophenol and exhibited excellent stability in cycling tests. Therefore, this study provides a new approach for synthesizing nanocomposites for various practical applications.