Acid-base bicentric ionic liquids catalytic reaction of EG and CO2 into carbonates enhanced by styrene oxide

In view of the harsh conditions of cyclic esterification reaction of ethylene glycol (EG) and carbon dioxide (CO2) to synthesize ethylene carbonate (EC), the yield is low and the catalysts are mostly metals, a series of green acid-base bicentric ionic liquids (ABbILs) were developed. Among them, the ABbILs of 1,5,7-Triazabicyclo[4.4.0]dec‑5-ene glutarimide ([TBDH][Glu]) had the best catalytic performance. Under the optimal reaction conditions, the yield of EC reached 29.5%, which was higher than most of the conventional metal-based catalysts. Through activity screening results and DFT calculation, it was found that different cations affect the interaction between N on anion and H proton of EG, and the H on the cation can activate the O on EG, which would affect the ability of ABbILs to activate EG. The acid-base bicentered synergistic catalytic mechanism of Bronsted acid and Lewis base was proposed by characterization and DFT calculation. This study opens up new avenues for the efficient conversion of diols and CO2 for the preparation of cyclic carbonates.