Synthesis of a heterogeneous 2D COF-based Fenton catalyst for epoxidation of olefins

Abstract

Styrene oxide is an important intermediate in many chemical syntheses. It can be produced through the epoxidation of styrene using supported metal catalysts. However, the catalytic performance and stability of these catalysts are negatively affected by the mass transfer, diffusional limitations and leaching of metals from supports. In this work, a hydroxyl-substituted bidentate 2D Schiff-base COF supported Fe₃O₄ particles catalyst (Fe-COF) is developed for styrene epoxidation using H₂O₂ as oxidant. Fe-COF catalyst possesses an eclipsed layered-sheet structure with a uniform distribution of Fe₃O₄ particles. Supported Fe₃O₄ particles as the active sites are responsible for the adsorption of styrene and generation of reactive oxygen radicals through the Fenton process. The presence of the extensive π-electron delocalization effect over COF support facilitates the electron transfer between Fe²⁺ and Fe³⁺ sites on Fe-COF catalyst during the reaction, accelerating the Fenton process, thus Fe-COF catalyst even shows a higher catalytic activity (86.0 % conversion of styrene and 88.0 % selectivity to styrene oxide) compared with homogeneous Fenton catalyst (Fe(NO₃)₃). In addition, Fe-COF catalyst demonstrates good stability after 5 recycles without Fe leaching, due to the coordination of Fe₃O₄ particles with the imine and hydroxyl groups in COF support.