Ultrafine silver nanoparticles supported on a covalent carbazole framework as high-efficiency nanocatalysts for nitrophenol reduction

Abstract

A novel conjugated microporous polymer (CMP) material CZ–TEB was synthesized with a carbazole analogue and 1,3,5-triethynylbenzene. It possessed a high specific surface area, excellent thermal stability and layered-sheet morphology. Furthermore, ultrafine silver nanoparticles were successfully immobilized on CZ–TEB, thus preparing a nanocatalyst Ag⁰@CZ–TEB. To evaluate its catalytic performance, Ag⁰@CZ–TEB was exploited in the reduction reaction of nitrophenols, a family of priority pollutants. Ag⁰@CZ–TEB exhibited high catalytic ability, convenient recovery and excellent reusability. Strikingly, the normalized rate constant (k_nor) of the reduction reaction of 4-NP to 4-AP is as high as 21.49 mmol⁻¹ s⁻¹. This result shows a significant improvement over all previously reported work. We purposed to use a “capture–release” model to explain the high catalytic ability of Ag⁰@CZ–TEB. This explanation is supported by further experimental results that agree well with the “capture–release” model.