Acidic pyridinium ionic liquid: an efficient bifunctional organocatalyst to synthesis carbonate from atmospheric CO2 and epoxide.

Ionic liquids (ILs) are used as non-toxic, biodegradable, non-volatile, and relatively low-cost catalysts to syn-thesize 5-membered cyclic organic carbonates (COCs) from carbon dioxide (CO2) and different types of oxiranes in great conversion and selectivity. Single-component IL containing pyridinium salt moieties as quaternary amine, the carboxylic functional group as a H-bond donor, and bromine as a nucleophile and significant leaving group was synthesized by a simple method. The simultaneous selection and use of all mentioned factors in IL caused the epoxides converted into their corresponding carbonates under mild conditions, under 1 atm carbon dioxide (CO2) pressure (CO2 balloon), co-catalyst/ metal/ and solvent-free during 2.5 h. The synthetic catalyst converted styrene oxide (SO) to styrene carbonate (SC) with 100% conversion and selectivity. Moreover, the catalyst could be recycled more than four times before losing its remarkable catalytic activity. Finally, an inferential mechanism was suggested according to the experimental results.

Automated summary

Ionic liquids are efficient catalysts with non-toxic, biodegradable, non-volatile, and low-cost properties for the synthesis of cyclic organic carbonates. The synthetic catalyst exhibited high conversion and selectivity under mild conditions without the need for co-catalyst, metal, or solvent. It could also be recycled multiple times before losing its catalytic activity.