In situ replacement of Cu-DEN: an approach for preparing a more noble metal nanocatalyst for catalytic use

Abstract

The advantage of dendritic monodisperse macromolecules’ dual templating ability was useful in the formation of silica-supported copper nanoparticles Cu_n@SiO₂NPs. This was acquired by the initial synthesis of a silica framework (G4-PAMAM-NH₂-SiO₂) as a mesoporous support using amine-terminated generation 4 PAMAM dendrimers (G4-PAMAM-NH₂). The encapsulated Cu_n@SiO₂ NPs, calcined at 500 °C, were made to undergo a displacement reaction with Au³⁺ generated from the equivalent molar addition of HAuCl₄. This resulted in the formation of Au_n@SiO₂NPs upon in situ replacement at a regulated pH. The synthesized nanoparticles were characterized and examined. The catalysts were shown to be catalytically active in the hydrogenation of 4-nitrophenol, and oxidation of rhodamine B as model reactions, before oxidation of styrene using TBHP. Also, the stability of the catalyst was evaluated, and the catalytic activity was retained after three consecutive cycles.