Polyimidazolium Salts: Robust Catalysts for the Cycloaddition of Carbon Dioxide into Carbonates in Solvent-Free Conditions

5 years ago

Polyimidazolium Salts: Robust Catalysts for the Cycloaddition of Carbon Dioxide into Carbonates in Solvent-Free Conditions

Zhaofu Fei, Wei Zhong, Paul J. Dyson, Felix D. Bobbink

There is a growing interest in sustainable heterogeneous catalysts based on organic polymers. Here, we describe a series of polyimidazolium salt catalysts, prepared from the direct reaction of arene-bridged bis- and tris-alkyl halides with trimethylsilylimidazole. The polyimidazolium salts were characterized by spectroscopic and analytical techniques and it was found that their morphology and porosity could be controlled by adjusting the steric parameters of the spacer in the alkyl-halide starting materials. Moreover, the polymers are excellent heterogeneous organocatalysts for the cycloaddition of CO2 to epoxides to afford cyclic carbonates at atmospheric pressure under solvent-free conditions. The polymer catalysts exhibit long-term stability and may be recycled and reused at least 10 times. Keeping it simple: Polyimidazolium salts containing aromatic linkers with differing steric demands are prepared in a single step from commercially available reagents. The polyimidazolium salts are efficient heterogeneous catalysts for the cycloaddition of CO2 into epoxides to form cyclic carbonates operating under ambient conditions. The polyimidazolium salts display prolonged lifetimes and are able to convert a range of different epoxides.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/cssc.201700570