Co(II), Fe(III) or VO(II) Schiff base metal complexes immobilized on graphene oxide for styreneepoxidation

Cobalt(II), iron(III) or oxovanadium(II) Schiff base metal complexes have been covalently grafted onto graphene oxide (GO) previously functionalized with 3-aminopropyltriethoxysilane. Potential catalytic behaviors were tested in the epoxidation of styrene, using air as the oxidant. The catalysts were characterized using infrared (IR) and Raman spectroscopies, thermogravimetric analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). IR spectroscopy, thermogravimetric analyses and ICP-AES confirmed the successful incorporation of the metal Schiff base complexes onto GO. X-ray diffraction, nitrogen adsorption-desorption, Raman spectroscopy, SEM and TEM showed the intact structure of the GO. Co-GO and Fe-GO showed high styrene conversion (90.8 versus 86.7%) and epoxide selectivity (63.7 versus 51.4%). Nevertheless, VO-GO showed poorer catalytic performance compared with Co-GO and Fe-GO. The recycling results of these heterogeneous catalysts showed good recoverability without significant loss of activity and selectivity within four successive runs. Copyright (c) 2015 John Wiley & Sons, Ltd.