Environmentally benign melamine functionalized silica-coated iron oxide for selective CO2 capture and fixation into cyclic carbonate

Abstract

The development of new materials capable of fixing CO2 into value-added products has become an exciting research field. Besides mitigating the rising level of CO2, such materials also enable CO2 as a C1 carbon source for useful industrial synthons. This article reports on the stepwise synthesis of a melamine functionalized silica-coated iron oxide (FSNM) material for selective CO2 capture and its catalytic conversion into a useful product. The synthesis of FSNM has been achieved by covalently grafting the melamine group in the pores of mesoporous silica-coated Fe3O4 (Fe3O4@SiO2) particle using isocyanate as a cross-linker. While the Fe3O4 core, owing to its superparamagnetic property, enables the easy retrieval of the material from the reaction mixture and, thus, enhances the recyclability, mesoporous silica coating offers a larger surface area for adsorption. The organic functionalities, containing melamine and carbamide moieties, facilitate the selective adsorption of CO2 on the material with a maximum CO2 uptake of 0.48 mmol/g at 1 bar and 298 K with excellent CO2/N2 selectivity. Moreover, the acid-base interactions between the acidic CO2 and basic amine groups enable the FSNM to catalyze the cycloaddition of CO2 with different epoxides to afford a series of cyclic carbonates, in the presence of tetrabutylammonium bromide (TBAB) as a co-catalyst, under facile and solvent-free conditions. These results strongly support that melamine functionalized Fe3O4@SiO2 affords new aspects towards environmentally friendly and recoverable hybrid adsorbent for adsorption and fixation of CO2 into the valuable products.