Synthesis of gold encapsulated in spherical carbon capsules with a mesoporous shell structure. A robust catalyst in a nanoreactor

•Mesoporous (Au@mSiO2) and macroporous (Au@SiO2) catalysts have been made.•The Au@mHCS yolk–shell composite reduced p-nitrophenol to p-aminophenol.•The Au@HCS did not reduce the p-nitrophenol.•A high temperature treatment of Au@mHCS (800 °C) did not affect the catalytic activity.•The Au@mHCS composite was reusable with no apparent drop in an activity (10 cycles).

Core-shell templates containing an encapsulated Au nanoparticle in a mesoporous silica (Au@mSiO2) or nonporous silica (Au@SiO2) shell structure were made. The silicas were then covered with carbon by CVD using toluene and the silica was removed using HF. Au@mHCS and Au@HCS were both characterized by PXRD, HRTEM, TGA, BET and ICP-OES. The Au@mHCS yolk–shell composite exhibited excellent catalytic activity and reusability (10 cycles) for the reduction of p-nitrophenol with conversion of up to 97% in 8 min. Heat treatment of Au@mHCS at 800 °C/4 h/N2 did not alter the morphology or the catalytic activity significantly.

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