Carbon dioxide, the gas widely associated with climate change, has been given a surprising new role by scientists: a safer source of oxygen in chemical reactions used to make medicines, plastics and fragrances.
An international research team, including scientists from the Jagiellonian University and the SOLARIS National Synchrotron Radiation Centre, has developed a light-driven process that uses CO₂ instead of more hazardous oxidising agents, which can increase the risk of fires and explosions and produce toxic waste.
The findings, published in the journal Science, show that even a highly stable molecule such as carbon dioxide can be activated for useful chemical reactions. The method could eventually help make some industrial processes safer and reduce reliance on more dangerous reagents.
Chemists do not only combine atoms to create larger molecules. Sometimes they must cut a molecule at a selected point and add oxygen to the resulting fragments. These fragments are then used to build drugs, plastics, fuels and fragrances. Reactions of this type account for nearly 30% of the chemical industry's production.
One important operation involves breaking a particularly strong bond between two carbon atoms. Ozone is used as chemical "scissors" for this purpose. Other methods require heavy metal compounds or large amounts of oxygen, increasing the risk of fire and creating additional waste.
The researchers turned to a substance that initially seemed unsuitable for the task: carbon dioxide.
CO₂, the end product of combustion, is extremely stable and reluctant to participate in further reactions because its oxygen atoms are strongly bound. However, this chemical stability also gives it an advantage: carbon dioxide is non-flammable and safer to handle than many strong oxidising agents.
The scientists prepared a solid material containing small amounts of iron. When illuminated with blue light, it acts as an intermediary between CO₂ and the molecule being processed.
A carbon dioxide molecule attaches to the iron atom and becomes activated, allowing oxygen to be transferred to the target molecule. After several further transformations, the original molecule breaks into two useful fragments.
"The process occurs at room temperature and normal pressure, without compressed oxygen or strong oxidisers," said Shoubhik Das from the University of Bayreuth, one of the study authors.
The method was tested on 45 different substances, including simple molecules prepared for the experiment as well as derivatives of drugs and hormones.
In a typical test, 82% of the expected product was obtained after 24 hours. The reaction was also carried out on a gram scale and in a continuous-flow device. The catalyst was reused ten times, although its efficiency decreased to 70%. In another experiment, the system operated for more than 21 days.
The researchers also had to prove that the oxygen used in the reaction came from CO₂. They used carbon dioxide containing a slightly heavier form of oxygen atoms as an invisible tracer. The labelled oxygen was later detected in the reaction products, confirming its transfer from the gas into the resulting substances.
The Polish contribution came from Professor Piotr Kuśtrowski from the Faculty of Chemistry of the Jagiellonian University and Lulu Alluhaibi, PhD, from the SOLARIS National Synchrotron Radiation Centre.
Using the powerful X-ray facilities at the SOLARIS National Synchrotron Radiation Centre in Kraków, the researchers analysed the catalyst to determine how the iron atoms were arranged and whether the material remained stable during operation.
The researchers acknowledge that the technology is still at an early stage. The experiments were performed on a small scale, required many hours and relied on chloroform, which produces problematic chlorinated waste.
Replacing the solvent, improving the speed of the reaction and increasing its scale will be necessary before the method can be considered for wider applications.
However, the study shows that even a molecule as chemically stable as CO₂ can be activated and used in controlled chemical reactions. If the remaining challenges are overcome, the method could reduce the use of hazardous substances and help make the production of chemicals used in medicines, plastics and other everyday products safer. (PAP)
PAP - Science in Poland
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