Solid-solid synthesis of covalent organic framework as a support for growth of controllable ultrafine Au nanoparticles

Covalent organic frameworks (COFs) are promising supports for the synthesis of noble metal nanoparticles (NM NPs) with controllable sizes and dispersities. However, it is still challenging to synthesize COFs using green and efficient routes. Herein, COFs (TpMA) were prepared by ball milling, which required less solvent and time. They were then used as a support for the growth of ultrafine Au NPs. Using the COFs as supports, five size-controlled ultrafine Au NPs (2.5 ± 0.55- 4.32 ± 1.39 nm) were synthesized (Au@TpMA). It was found that the Au NPs exhibited remarkable dispersibility owing to the support of TpMA. The reduction of 4-nitrophenol to 4-aminophenol was used as a model reaction to evaluate the performance of the Au@TpMA catalyst, which showed excellent catalytic activity for the reduction of 4-nitrophenol. The Au@TpMA catalyst exhibited good stability and recyclability, and the reduction rate was 95% at the end of six successive experiments. In addition, in the presence of the Au@TpMA catalyst, the maximum pseudo-first-order reaction rate constant of 4-nitrophenol was 0.2379 min-1. From the results of this study, we hope that using COFs-based supports prepared by ball milling for the size-controlled synthesis of NM NPs provides a path forward for the mechanical synthesis of other COFs.