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 as PowerPoint slide