Molecules soak up greenhouse gases
Greenhouse gases (GHGs) are gases that absorb and emit radiation within the thermal infrared range in Earth’s atmosphere but not radiation in or near the visible spectrum. The primary GHGs are water vapour, carbon dioxide, methane, nitrous oxide and ozone. Carbon dioxide being one of the most abundant GHGs causes the biggest problem. However there are several other compounds which are thousands of times more potent in their greenhouse effect per unit of mass. These compounds include Freons, used as common refrigerants, and fluorocarbons, highly stable organic compounds in which one or more hydrogen atoms have been replaced with fluorine.
GHGs have a huge impact on Earth’s temperature. Without them, Earth’s surface would be colder on an average of about 33 °C than present temperature on Earth. Burning of fossil fuels and extensive clearing of native forests has contributed to a 40% increase in the atmospheric concentration of carbon dioxide and other GHGs. This would impart huge impact on most ecosystems on Earth and the livelihoods of over 3 billion people worldwide. The GHGs also triggerocean bio-geochemical changes with broad ramifications in marine systems.
A team of chemistry researchers from University of Houston (UH), University of Chicago and Taiwan National Synchrotron Radiation Research Centre have developed a molecule that assembles spontaneously into a lightweight structure with microscopic pores capable of binding large quantities of several potent GHGs. A fluorinated backbone forms the structure of this molecule containing extremely small pores about 1.6 nanometers in diameter. These tiny pores are lined with fluorine atoms, giving them a high affinity for other fluorine containing molecules like, fluorocarbons and Freons. Fluorocarbons have very long lifetime (e.g. lifetime of tetrafluoromethane and hexafluorometahne are 50,000 and 10,000 years respectively) and thus have a very long lasting deleterious effect on our climate.
Porous materials with similar pore sizes have been developed is not a new concept. But the materials developed earlier were often heavy, as they contained metals, and sensitive to water. Thus they were relatively difficult to process and recycle.
The new material is advantageous in several aspects. It is stable to water. There are no metal connectors and thus is lightweight. The individual molecules are held together by weak interactions, therefore the interactions between the molecules can be broken when required, and can be recycled or deposited on a surface very easily. The molecule is stable at high temperatures (up to 280 degrees Celsius).
A provisional patent based on this work has been filed.
Thermally robust and porous noncovalent organic framework with high affinity for fluorocarbons and CFCs.Teng-Hao Chen, Ilya Popov, Watchareeya Kaveevivitchai, Yu-Chun Chuang, Yu-Sheng Chen, Olafs Daugulis, Allan J. Jacobson, Ognjen Š. Miljanić. Nature Communications, 2014; 5: 5131 DOI:10.1038/ncomms6131
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