Highly Crystalline Mesoporous Titania Loaded with Monodispersed Gold Nanoparticles: Controllable Metal-Support Interaction in Porous Materials.

We report the syntheses of mesoporous Au/TiO2 hybrid photocatalysts with ordered and crystalline frameworks using co-assembly of organosilane-containing colloidal amphiphile micelles (CAMs) and poly(ethylene oxide)-modified gold nanoparticles (AuNPs) as templates. The assembled CAMs can convert to inorganic silica during calcination at elevated temperatures, providing extraordinary thermal stability to preserve the porosity of TiO2 and the nanostructures of AuNPs. Well-defined AuNPs supported within mesoporous TiO2 (Au@mTiO2) can be prepared using thermal annealing at temperatures up to 800 °C. High-temperature treatment (≥500 °C) under air is found to not only improve the crystallinity of TiO2 but also induce oxidative strong metal-support interactions (SMSIs) at Au/TiO2 interfaces. For oxidative SMSIs, the surface oxidation of AuNPs can generate positively charged Auδ+ species, while TiO2 gets reduced simultaneously. Using photocatalytic oxidation of benzyl alcohol as a model reaction, Au@mTiO2 calcined at 600 °C for 12 h exhibited the best activity under UV irradiation, while Au@mTiO2 calcined at 600 °C for 2 h showed the best activity under visible light. The delicate balance between the crystallinity and porosity of TiO2 and the SMSIs at Au-TiO2 interfaces is found to impact the photocatalytic activity of these hybrid materials.