Ionic Nanoparticle Networks as Solid State Catalysts

We report on the catalytic activity for the cycloaddition of CO2 to cyclic organic carbonates of recently developed ionic nanoparticle networks (INN). The combination of high imidazolium content and ability to coordinate to CO2 molecules within the 3D network makes the hybrid INN materials highly promising heterogeneous catalysts for CO2 activation reactions. The catalytic activity of INN powders and gels was investigated with various starting epoxides. Quantitative conversion was reached with epichlorohydrin. The influence of mono or bis(imidazolium) bridging ligands and methylation at the C2 position in the aromatic ring of the organic cation could be highlighted by evaluation of the activity with the less reactive propylene oxide as the starting epoxide. Finally, the influence of the type of inorganic nanoparticle support was also studied by preparing heterobimetallic silica-zinc oxide nanoparticle networks. Promising results were obtained with various epoxides. Conversion or selectivity up to 100 % could be obtained. The catalyst could be reused owing to the good thermal stability of the hybrid inorganic-organic INN. After four reaction runs the catalyst still proved to be active.