Researchers at the Universitat Jaume I (UJI) have developed a new catalyst for the "activation" of carbon-fluorine bonds. This process has many industrial applications, among which stands out the possibility to be used to reduce existing stocks of CFCs (chloro-fluoro-carbonated compounds), known as "greenhouse gases." CFCs experienced a huge boom in the 80s, but later they were found to destroy the ozone layer because of their photochemical decomposition when they reached the upper layers of the atmosphere.
The Organometallic Chemistry and Homogeneous Catalysis Group coordinated by Eduardo Peris at the UJI has developed "the most active catalyst that exists so far for the activation (in chemical jargon, "break") of carbon-fluorine bonds, which are the strongest bonds in organic molecules, and also the most difficult to break; hence the great difficulty of decomposing organic fluorinated compounds." The relevance of the results obtained has led the work, co-directed by Dr. José A. Mata and with the participation of the doctoral student Sara Sabater, to be published in the prestigious journal Nature Communications. There, the article has received nearly a thousand views in less than a month. The work provides an added value for the Universitat Jaume I in Castelló, since it has been entirely developed by three UJI researchers.
Due to their high stability, CFCs experienced a great development during the 80s, mainly for their application in products such as aerosols, fridge gas, etc., until their high detrimental effect was evident: when they reach the atmosphere, by the action of the sun, they decompose creating free radicals that destroy the ozone layer. This discovery caused that a lot of volatile CFC compounds remain in stock, unable to be eliminated due to the high energy costs that it entails. "Thus, we have to try to transform them into less harmful products. Replacing fluorine by hydrogen is a desirable but extremely complicated process due to the inertia of the carbon-fluorine bond," explains the Professor of Inorganic Chemistry. The developed catalyst is very active and effective to perform a controlled destruction of such compounds.
The design of the catalyst arises from a conceptually very simple idea: the combination of two different metals that act synergistically. Thus, one of the metal breaks the carbon-fluorine bound (palladium), and the other introduces hydrogen (ruthenium). The idea has generated a great excitement in the specialized forums. The exploitation of heterometallic catalysts (with two different metals) has already placed the UJI's research group at the international forefront of research in catalysis, since the use of heterometallic catalysts enables to sequentially concatenate catalytic processes, and this facilitates obtaining very sophisticated molecules minimizing costs and simplifying the experimental procedures.
The group is now working on a new phase of research to facilitate the reverse reaction. "If a catalyst causes a reaction in one direction, it also has to run in the opposite direction. It is what is called 'principle of microscopic reversibility'. In other words, we are now changing carbon-fluorine by carbon-hydrogen and, in theory, the opposite step could also be done. That would facilitate introducing fluorine into other compounds and open up huge possibilities. It would be a big step because it is an extremely difficult reaction. The preparation of fluorinated molecules could have a great impact in different fields, such as in the pharmaceutical industry for drug development. This would be one of the many paths that may be opened if we reach this reverse reaction."
- Sara Sabater, Jose A. Mata, Eduardo Peris. Hydrodefluorination of carbon–fluorine bonds by the synergistic action of a ruthenium–palladium catalyst. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3553
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