Gold nanoparticles grown on a hydrophobic and texturally tunable PDMS-like framework

Abstract

Mesoporous silicas are among the most suitable high-surface area solids to support small-sized metal clusters and nanoparticles. Unfortunately, the instability of silica in water constitutes a serious impedement for its massive use and large implementation as catalytic support for fine chemical synthesis and for biomass upgrading in the context of the biorefineries. While silica hydrophisation provides a way for delaying the framework degradation, further investigations are needed to design more robust, water-resistant supports. Prompted by the success of polydimethylsiloxane (PDMS) in surface coating and water-repellent technologies, we herein explore the transformation of triethoxysilyl-functionalized polymethylethylsiloxane - a sol-gel analogues of PDMS - into hydrophobic desordered mesoporous MCM-41-type siloxane framework. The concomitent addition of soluble gold precursor during the mesophase formation followed by surfactant removal resulted in the entrapment and growth of gold nanoparticles inside. Thermally-induced evolution of the PDMS-like siloxane framework was further investigated both under inert and open air atmosphere. Gold accessibility was ascertained during the transformation of nitrophenol, a harmful water pollutant, into aniline as a valuable amine-based precursor. Owing to the virtues of PDMS-like framework for slowing down water and oxygen diffusion, the catalysts preserve their activity even after 18 month storage under open air atmosphere.