Fabrication of Carboxylic Acid and Imidazolium Ionic Liquid Functionalized Porous Cellulosic Materials for the Efficient Conversion of Carbon Dioxide into Cyclic Carbonates

Abstract

Cellulosic poly(ionic liquid)s ([Cellmim][Br]) with a degree of substitution (DS) in the range of 0.32–0.89 were synthesized successfully via the homogeneous transesterification reaction of cellulose with 1-(2-methoxyacetyl)-3-methyl imidazole bromide IL ([Mmim][Br]) in a DBU/DMSO/CO2 solvent system. The structure and properties of these novel materials have been fully characterized. Cellulosic poly(ionic liquid) POF polymers (POF-[Cellmim][Br]) were then obtained by an in situ crosslinking reaction without adding an exterior catalyst. The porosity and properties of the POF-[Cellmim][Br] materials can be modulated. The POF-[Cellmim][Br] materials functioned as green, efficient, and highly active catalysts for cycloaddition reactions of epoxides and carbon dioxide under solvent-free and co-catalyst-free conditions. These reactions gave high yields (up to 97%), and the catalyst can be easily separated with excellent reusability and no significant change to its structure. A plausible reaction mechanism for the cycloaddition reaction of epoxide and carbon dioxide by the POF-[Cellmim][Br] catalyst is proposed based on the experimental results. This work provided a new strategy to prepare cellulosic-PIL POF materials and offered a platform to understand the cooperative effects of porous properties and nucleophilic anions on the cycloaddition reaction of carbon dioxide and epoxides.