Adenine-Functionalized Dendritic Fibrous Nanosilica as Bifunctional Catalyst for CO2 Fixation into Cyclic Carbonate

Abstract

Cycloaddition of CO2 with epoxide to form cyclic carbonate is one of the most promising approaches to mitigate the rising level of CO2 in the atmosphere. Therefore, the design and synthesis of new materials which can efficiently catalyze such reactions has become an important research area. This article reports on the synthesis of a new material, adenine functionalized dendritic fibrous nanosilica (DAD), by functionalizing the surface of dendritic fibrous nanosilica (DFNS) with an N-containing heterocyclic nucleobase adenine using a bifunctional isocyanate crosslinker ((EtO)3Si(CH2)3NCO). The surface amine functionalities enable DAD to show selective CO2 adsorption (0.44 mmol/g, at 1 bar CO2 pressure and 298 K temperature) due to acid-base interaction between CO2 and amine groups. Moreover, DAD efficiently catalyzes the fixation of CO2 with a variety of epoxides into corresponding cyclic carbonates in the presence of TBAB (tetrabutylammonium bromide) co-catalyst under solvent-free conditions. The DFNS skeleton of DAD offers a high surface area for enhanced CO2 adsorption, while its organic surface groups, adenine and carbamide, boost the selectivity and activate the epoxide ring and CO2 for cycloaddition reaction. The strong covalent linkage of surface groups in DAD renders robust structural integrity, enabling the catalyst to be recycled multiple times with negligible reduction in its catalytic performance. © 2023 Wiley-VCH GmbH.