The emission of greenhouse gases contributes significantly to global warming. Not only carbon dioxide (CO .)2) but fluorinated gases – including so-called anti- or polyfluorinated hydrocarbons, or PFCs – have a significant share in this development. Pro. Researchers at the Institute of Organic Chemistry at Heidelberg University, led by Dr. Michael Mastlerz, have recently developed new crystalline materials that can selectively adsorb molecules of such carbon-fluorine bonds. The Heidelberg researchers hope that these porous crystals may be useful for targeted binding and recovery of PFCs.
Polyfluorinated carbons are organic compounds of various lengths in which the hydrogen atoms of alkanes are partially or completely replaced by fluorine atoms. These atoms are chemically highly stable. They are not ubiquitous in nature and are used primarily as a contrast enhancer for etching procedures in the semiconductor industry, in ophthalmic surgery, and for some ultrasound examinations in medical diagnostics. “The opposite of CO2which is integrated into natural physical cycles, PFCs accumulate in the atmosphere and remain there for many thousands of years before breaking down.” Compared to carbon dioxide, PFCs have a much greater global warming potential – the effect of a PFC molecule by about 5,000. 10,000 CO is equal to2 Molecule. According to the researcher, this makes polyfluorinated hydrocarbons a permanent problem that is not only contributing to global warming but also accelerating it.
Together with his research group at the Institute of Organic Chemistry of the University of Heidelberg, Prof. Mastlerz has developed a new type of crystalline material that can absorb polyfluorinated hydrocarbons highly selectively, that is, bind them to its inner surface. The porous crystals are based on shape-stabilizing organic cation compounds that carry fluorine-containing side chains on interconnected struts. These side chains react according to the “like attracts” principle through fluorine–fluorine interactions with PFC molecules, ensuring that they are deposited on the inner surface of the material. In their experiments, the Heidelberg researchers proved that the crystals they developed bind some fluorine-containing gases, such as octafluoropropane or octafluorocyclobutane, about 1,500 to 4,000 times more strongly than dinitrogen, the main component of air. Pro. According to Mastlerz, these numbers represent an exceptionally high selectivity to force such PFCs.
Presently Prof. Mastlerz and his team are working on further enhancing the crystal’s selectivity and transferring this process to other fluorinated gases, such as those used in medical anaesthesia. “I see great potential for development in this area,” emphasizes the researcher. He hopes that the adsorbent can be used to recover polyfluorinated hydrocarbons in place of their use.
The German Research Foundation funded the research.
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