Functionalized graphene oxide as an efficient adsorbent for CO2 capture and support for heterogeneous catalysis

Abstract

We have designed new imine-functionalized graphene oxide (IFGO) through post synthetic modifications involving co-condensation of 3-aminopropyltriethoxysilane with graphene oxide basal plane containing hydroxyl and epoxy functional groups, followed by Schiff base condensation reaction with 2,6-diformyl-4-methylphenol and impregnation of copper(II) to it through covalent attachment (Cu-IFGO). Powder X-ray diffraction, N₂ sorption analysis, FT-IR, HR-TEM, FE-SEM and TGA/DTA analysis are employed to characterize the materials. The IFGO material exhibits good CO₂ storage capacity of 8.10 mmol g⁻¹ (35.64 wt%) and 2.10 mmol g⁻¹ (9.24 wt%) at 273 K and 298 K temperature, respectively, up to 3 bar pressure, suggesting its potential application in environmental clean-up. Also, Cu-IFGO showed high catalytic activity in microwave-assisted one-pot three-component C–S coupling reactions for a diverse range of aryl halides with thiourea and benzyl bromide in aqueous medium to obtain aryl thioether products (maximum yield 86%), which are derivatives of natural products. Moreover, having imine and hydroxyl groups in functionalized graphene oxide, the grafted Cu(II) chelated at the graphene oxide surface so strongly that it could not be leached out from the material during the course of the coupling reaction. Thus, it displayed very small decrease in product yield up to the sixth reaction cycle suggesting a sustainable future of this Cu(II)-grafted catalyst.