OICC Press Iranian Journal of Catalysis 2345-4865 8 2 2024 02 03 An environmentally friendly approach to the synthesis of azo dyes based on 2-naphthol using kaolin-SO3H nanoparticles EN Abdolhamid Bamoniri Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, Iran 0000-0002-8911-2433 Bi Bi Fatemeh Mirjalili Department of Chemistry, College of Science, Yazd University, Yazd, P.O. Box 89195-741, Iran 0000-0002-6588-4041 Nahid Yaghmaeiyan-Mahabadi Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, Iran Journal Article 2024 02 03 Kaolin-SO3H nanoparticles were prepared via reaction of kaolin and chlorosulfonic acid and characterized by FT-IR, XRD, FESEM, TEM, XRF, EDS, BET and TGA. The activity of this green catalyst was probed by the synthesis of aryl diazonium salts as the starting reactant and then, their diazo coupling with  2-naphthol to form azo dyes in a solvent-free medium at room temperature. The work-up of the reaction was easy, and the catalyst was removed from the products by simple filtration. The reaction proceeded in a short time, easy purification technique, high yields, and was environmentally friendly furthering approaches to green chemistry. The products were characterized by FT-IR and NMR spectroscopy.