Researchers have developed a variety of powerful catalysts called superacids that can turn harmful materials such as greenhouse gases and certain hydrocarbons into useful chemicals.
The work by researchers at Paderborn University in Germany succeeds in producing superacids called "Lewis superacids," or LSAs, which until now have been notoriously difficult to create, they said. These superacids can add electron pairs, which gives them the ability to speed up chemical reactions, the researchers from the university's Department of Chemistry and Center for Sustainable Systems Design (CSSD) said.
Lewis superacids also are stronger than antimony pentafluoride, which is the strongest Lewis acid. This means they can break even the toughest bonds, said Professor Jan Paradies from the university's Department of Chemistry. This capability paves the way for their use to convert non-biodegradable fluorinated hydrocarbons, similar to Teflon, and possibly even climate-damaging greenhouse gases, such as sulphur hexafluoride, back into sustainable chemicals, he said.
“For strong bonds, you need highly reactive reagents, i.e., substances that are extremely reactive," Paradies explained. The new catalyst can split, for example, carbon-fluorine or sulphur-fluorine bonds, which are particularly robust, he said.
Facilitating Production and Use of Superacids
Lewis superacids intrinsically and thus historically are incredibly reactive, which makes them difficult to produce and use, Paradies said. However, the researchers used a trick to produce these molecules so they can be used in catalytic reactions, which they also demonstrated.
To produce the superacids, researchers used an electrochemical produce that leveraged redox-active materials as well as boranes carrying peripheral cationic groups or cationic boranes, they explained in a paper on their work published in the journal Angewandte Chemie.
"It was envisaged that the synthesis and handling of potential LSAs might be tremendously simplified by applying redox processes at a late stage or, e.g., just prior to catalytic application," they wrote. "The ferrocenyl group (Fc) is a widely recognized reversible redox-active group and had the potential to build the Lewis acid we sought."
Through their research, the team applied ferrocenyl/ferrocenylium boranes and boronic esters to catalyze challenging bond activations and form the Lewis superacids, they said.
The researchers hope their work can be used in the future to contribute to the sustainable use of resources not only in scientific research, but also to demonstrate to future scientists the possibilities for sustainability in an educational setting, Paradies said.
“We’re thereby placing a clear emphasis on sustainability not only in research, but also in teaching," he said.