Cooperative Conversion of CO2 to Cyclic Carbonates in Dual-Ionic Ammonium Salts Catalytic Medium at Ambient Temperature

Novel metal-free, dual-ionic ammonium salts catalytic media were developed, and they were used to catalyze the cycloaddition of CO2 and epoxides to yield cyclic carbonate. The effects of catalyst structures and reaction parameters on the catalytic activity were investigated. The optimized [TEA(+)O(2)(-)][Br-][DBUH+] contains hydrogen-bond donor groups (-NH), nucleophilic [Br-] and carboxyl anions, and it shows exceptional catalytic performance with satisfied product yield and selectivity at ambient temperature due to the synergy between the dual cations and anions in the system. The present catalyst exhibits good reusability and can keep excellent activity after five reaction cycles. The catalyst also shows general applicability to other epoxide substrates. Finally, an insight into the dual cation-anions synergetic activation pathway and catalytic mechanism was proposed.