Luffa sponge supported dendritic imidazolium ILs with high-density active sites as highly efficient and environmentally friendly catalysts for CO2 chemical fixation

Abstract

Efficient using of green heterogeneous catalysts from renewable natural sources through chemical modification for the cycloaddition of terminal epoxides with CO2 is attractive but still challenging. Luffa sponge is a cheap, biodegradable, abundant and renewable source with netting-like three-dimensional porous structure. Herein, we report a simple and facile approach to the preparation of a series of novel luffa sponge-supported dendritic imidazolium ILs heterogeneous catalysts LS-DIL-(G1-G3) with high ionic density from natural luffa sponge fibers. LS-DIL-(G1-G3) were properly characterized by FT-IR spectroscopy, TGA, elemental analysis, and SEM. Among them, LS-DIL-G3 was found to exhibit the highest catalytic activity for the synthesis of cyclic carbonates under metal-free and solvent-free conditions. It was clearly observed that there was a positive dendritic effect on the yields of cyclic carbonates. Furthermore, a wide range of terminal epoxides was converted smoothly to the corresponding cyclic carbonates with high yields (84–99 %). LS-DIL-G3 could be reused for up to six consecutive runs without any obvious decline in catalytic activity. Importantly, the desired cyclic carbonates could be prepared on a multigram scale by using LS-DIL-G3 as a green heterogeneous catalyst.