Two new magnetic nanocomposites of graphene and 12-tungestophosphoric acid: characterization and comparison of the catalytic properties in the green synthesis of 1,8-dioxo-octahydroxanthenes

Abstract

Two well dispersed H₃PW₁₂O₄₀ immobilized to magnetite graphene oxide (Fe₃O₄/GO/PW) and magnetite graphene aerogel (Fe₃O₄/GA/PW) nanocomposites were synthesized, via coprecipitation and coprecipitation-solvothermal methods, respectively. The catalytic activity, leaching and recyclability of the two prepared catalysts were compared in the synthesis of 1,8-dioxo-octahydroxanthenes (DOX) in water. Fe₃O₄/GO/PW showed higher activity, and lower leaching followed by a higher reusing number compared with Fe₃O₄/GA/PW. The as-prepared Fe₃O₄/GO/PW nanocomposite was fully characterized by transmission electron microscopy, scanning electron microscopy, a vibrating sample magnetometer, energy dispersive X-ray spectroscopy, X-ray diffraction, laser particle size analyzer, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The excellent conversions show that the catalyst has been used as a highly effective catalyst for the synthesis of DOX. The novelty of this catalyst is the low leaching of PW in aqueous media and reusability of the catalyst for at least four times with an appreciable loss of its catalytic activity.