By Zimeng “Parker” Xie | December 4, 2012 3:00 pm

What? Trapping gases? Are you a balloon dealer or just out of your mind?

Many people might wonder how to trap something that slips through fingers, but it’s actually not that hard. Modern technology – chemistry, material sciences, and so on – has provided us with tons of ways to detain gases, especially harmful ones, such as carbon dioxide that causes global warming and sulfur dioxide which smells like tear gas (Ugh!) and is responsible for acid rain that wears off buildings, metal pipes, and statues. Mainly produced by factories since the industrialization, these two kinds of gases are causing big troubles: icebergs of Polar Regions are melting at ever-increasing rates, trees, and statues are being corroded, and the growth of vegetation and crops are being threatened. Even worse, in the winter of 1952, an incidence of SO2 smog in London killed thousands of people, with even more victims suffering from severe lung diseases induced by the smog.  But scientists are striving to stop this.

A group of chemists and environmental scientists at Nottingham University have found that a type of solid they synthesized in the laboratory, named NOTT-300, possesses excellent capabilities of trapping CO2 and SO2 molecules. This solid is classified as porous metal-organic framework (MOF) complex, a type of new material with structures somewhat similar to loofah sponges that shows promise for the exhaust gas treatment in future. By attracting carbon dioxide and sulfur dioxide through weak hydrogen bonding, NOTT-300 is able to attract these molecules into holes inside it and retain them as well. Compared with similar MOFs, NOTT-300 has outstanding selectivity and sensitivity with regard to CO2 and SO2 among a variety of gases such as hydrogen, nitrogen, and argon, which means that the vast majority of the gas molecules it attracts would be carbon and sulfur dioxide.  Plus, the thermodynamics feature of NOTT-300 enables a lower energy penalty to re-release the gas molecules for proper treatment, resulting in higher efficiency and better eco-friendliness compared to traditional, amine-based MOFs. In other words, NOTT-300 traps a good amount of carbon dioxide and sulfur dioxide without dealing with other common gases in the atmosphere, such as oxygen and nitrogen; besides, it is much easier to clean up NOTT-300 than other materials after it did the work.

Structure of NOTT-300-solvate.

Fig. 5 The structure of NOTT-300

In order to dig deeper on how NOTT-300 works, the research group performed additional experiments. A novel analytical method called inelastic neutron scattering (INS) was used to determine the structure and co-relationship between the material and the trapped gas molecules due to the imperfectness of structure of microcrystals of the adsorption material. In other words, because gas molecules are trapped in the holes of the material, simply taking a photograph outside would not tell us much; rather, we should perform an X-ray examination to see what’s going on inside – which is why the research group carried out high resolution X-ray diffraction to understand the adsorption mechanism in a more in-depth way. From these studies, researchers found out that the mechanisms for exhaust gas molecules to stay in the material is more complex than they thought – multiple ways of trapping have been detected, and they are still investigating on how these ways could work together.

To conclude, NOTT-300 is like a vacuum cleaner with a remote control that comes in handy – its attraction of target gas molecules is “easy-on, easy-off”, enabling its potential users to control the trapping process easily as compare to the traditional materials that “stick” with the gas molecules. And these scientists are not compromising anything – including effectiveness, eco-friendliness, and accuracy – in the synthesizing, experimenting and applying of their next-generation material that might solve huge environmental problems (Yang et al.).

Further Readings

How Carbon Capture Works

References

  1. [Factories emitting exhaust gas]. 2012. ZME Science. JPG File.
  2. [Icebergs melting]. 2011. Michael Brown. JPG File.
  3. [Trees damaged by acid rain]. 2012. National Geography. JPG File.
  4. [Statues damaged by acid rain]. 2012. Wikimedia. JPG File.
  5. Yang, S., Sun, J., Ramirez-Cuesta, A. J., Callear, S. K., David, W. I. F., Anderson, D. P., Newby, R., et al. (2012). Selectivity and direct visualization of carbon dioxide and sulfur dioxide in a decorated porous host. Nature Chemistry, 4, 887–894.

Categorized under: Environmental pollution, Chemistry, Material Sciences

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