Aliphatic carboxylic acid as a hydrogen-bond donor for converting CO2 and epoxide into cyclic carbonate under mild conditions

The coupling of CO2 and epoxides is a promising way to reduce atmospheric carbon by converting it into value-added cyclic carbonate. Pursuing efficient catalysts is highly attractive for the title reaction. Herein, we developed simple and inexpensive catalyst systems of aliphatic carboxylic acids as the hydrogen-bond donor (HBD) and quaternary ammonium halides as the nucleophile to catalyze the CO2-epoxide coupling reaction with high efficiency and selectivity under mild conditions (80 degrees C and 4 bar CO2). The high activity of this catalyst system is retained even under ambient conditions. The effects of the acidity and steric hindrance of acids on the catalysis of CO2-epoxide coupling were systematically investigated. Lastly, the reaction mechanism was deduced and its rationality was further reinforced by exploring the interaction between a representative system AA/TBAB (acetic acid/tetrabutylammonium bromide) and propylene oxide (PO). The study of aliphatic carboxylic acids/quaternary ammonium halides provides a new way to design catalyst systems for the title reaction.

Automated summary

The study developed a simple and inexpensive catalyst system using aliphatic carboxylic acids and quaternary ammonium halides as catalysts to efficiently catalyze the coupling of CO2 and epoxides. The research systematically investigated the effects of acid acidity and steric hindrance on the catalysis and deduced the reaction mechanism through exploring the interaction between representative systems.