β -Cyclodextrin polymer networks stabilized gold nanoparticle with superior catalytic activities

Support materials play a significant role in heterogeneous nanocatalysis. In this work, β-cyclodextrin (β-CD) was used directly as a monomer to construct polymer networks for gold nanoparticles (Au NPs) immobilization. Using the simple nucleophilic substitution reaction, β-CD based polymer networks (β-CDP-N and β-CDP-C) were successfully prepared. Compared to β-CDP-C, the hydroxyl groups and N atoms in β-CDP-N played a synergistic role in immobilizing smaller Au NPs, thus leading to high catalytic activities. Notably, the apparent rate constant (Kapp) value for Au@ β-CDP-N in the reduction of 4-nitrophenol to 4-aminophenol is 14.15 × 10−2 s−1, which shows a significant improvement over all previously reported Au NPs with solid supports under similar conditions. Considering the negligible porosity of the β-CDP-N support, we purposed a “capture-catalysis-release” model to explain the high catalytic activity of Au@ β-CDP-N. This explanation is supported by the guest-responsive properties of β-CDP-N. Moreover, the Au@ β-CDP-N is easily recycled and maintained its high catalytic efficiency after seven successful cycles.