Heterogeneous Recyclable Fiber-Supported TEMPO Catalyst for Highly Selective Aryl Alcohols Oxidation

2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) has been widely employed as a catalyst in various homogeneous and heterogeneous catalytic systems. By immobilizing TEMPO with polyacrylonitrile fiber (PANF) through a Michael addition reaction, TEMPO-functionalized PANF (PANTPF) as an efficient and recyclable catalyst was successfully synthesized and characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and mechanical strength analysis. The experimental results demonstrated that PANTPF is a readily recyclable catalyst that can be employed for the oxidation of a diverse range of alcohols. It exhibited remarkable catalytic efficiency in the selective oxidation of benzyl alcohols to benzaldehydes or phenones, with conversion up to 100% and selectivity exceeding 90%, and both parameters remained at a high level throughout the five runs. Additionally, a two-step covalent modification allows for the convenient preparation of this catalyst. Furthermore, the oxidation of alcohols was conducted in an aqueous system with sodium hypochlorite serving as the oxidizing agent, obviating the necessity for additional phase transfer catalysts. Overall, PANTPF offers several advantages, including easy preparation, excellent recycling performance, and high conversion and yield. Moreover, the catalyst can be readily separated and recycled, indicating its significant potential for use in both laboratory and industrial applications.