Crystal materials could effectively absorb carbon-fluorine bonds

Global warming caused by greenhouse gas emissions is considerable. Gases containing fluorine, such as the so-called perfluorinated or polyfluorinated hydrocarbons, or PFCs, as well as carbon dioxide (CO2), play a crucial role in this process.

In the background: optical microscopy images of the single crystal structures of the shape-persistent organic cage compound. On the front: ball-and-stick model of the monocrystalline structure, gray: carbon, white: hydrogen, red: oxygen, blue: nitrogen, green: fluorine. Image credit: Prof. Dr. Michael Mastalerz.

New crystalline materials capable of specifically adsorbing molecules with such carbonfluorine bonds have recently been produced by scientists at the Institute of Organic Chemistry of the University of Heidelberg under the direction of Professor Dr. Michael Mastalerz. The Heidelberg researchers hope that PFCs can be specifically bound and recovered from these porous crystals.

Polyfluorinated carbons are chemical compounds of varying lengths in which fluorine atoms have partially or completely replaced the hydrogen atoms of alkanes. Chemically, these atoms are quite stable. They are not often found in nature and are mainly used for etching procedures in the semiconductor industry, eye surgery and in the field of medicine as contrast enhancers for certain ultrasound diagnostics.

Unlike CO2integrated into the natural cycles of materials, PFCs accumulate in the atmosphere and remain there for several thousand years before degrading.

Dr. Michael Mastalerz, Professor, Institute of Organic Chemistry, University of Heidelberg

PFCs therefore have a considerably higher global warming potential than carbon dioxide since one PFC molecule has an effect that is roughly equivalent to 5,000 to 10,000 CO2 molecules. Therefore, polyfluorocarbons, according to the researcher, become a persistent problem that both causes and exacerbates global warming.

Professor Mastalerz has created a new type of crystalline material capable of very selectively attaching polyfluorocarbons to its inner surface with the help of his research team at the Institute of Organic Chemistry of the University of Heidelberg. Shape-persistent organic cage structures that carry fluorine-containing side chains on bonded struts serve as the basis for porous crystals.

Through fluorine-fluorine interactions with the PFC molecules, these side chains react according to the “like attracts like” principle and ensure their coating on the internal surface of the material.

The Heidelberg scientists have established through their research that the crystals they have generated bind certain fluorine-containing gases such as octafluoropropane or octafluorocyclobutane 1,500 to 4,000 times more strongly than nitrogen, the main component of air. . These figures reflect very high selectivities for binding these PFCs, according to Professor Mastalerz.

Currently, Prof. Mastalerz and his group are focusing on increasing crystal selectivity and adapting the procedure to different fluorinated gases, including those used in patient anesthesia. “I see huge development potential in this area“, emphasizes the researcher.

Professor Mastalerz hopes that polyfluorocarbons can be recovered at the point of application using the adsorbent.

The study was funded by the German Research Foundation.

Journal reference:

Tian, ​​K., et al. (2022) Highly selective adsorption of perfluorinated greenhouse gases by porous organic cages. Advanced materials.


Garland K. Long