TiO2-based green heterogeneous catalysts for the cycloaddition of CO2 to epoxides

TiO2 doped with metal ions (M-TiO2, M = Zn2+, Cu2+, Co2+, Mn2+, or Ni2+) was investigated as a heterogeneous catalyst for the coupling reaction of CO2 and epoxides, using tetrabutylammonium iodide (TBAI) as a co-catalyst under solvent-free conditions. These compounds were found to exhibit high catalytic activities. The effects of reaction temperature, reaction time, and CO2 pressure on the effectiveness of a Zn-TiO2/TBAI catalyst system were also examined. Zn-TiO2 represents a nontoxic, heterogeneous catalyst that can be reutilized up to five times without a significant loss of catalytic activity.

Graphical AbstractZn2+-TiO2 was investigated for the green catalysis of the coupling of CO2 and epoxides under mild conditions and was found to generate cyclic carbonates in high yields.Figure optionsDownload full-size imageDownload as PowerPoint slide