Organic gas traps could pull new industry from thin air
Tiny organic cages could be used to extract rare, valuable and sometimes deadly gases from the air.
The new material represents a big breakthrough in the ability to pull gases such as radon, xenon and krypton out of the air.
The rare elemental gases all occur naturally in the air but in tiny quantities – usually less than one part per million.
The gases are extremely expensive to extract from the air, requiring the use of cryogenic technology.
But in industries which use heavy lighting or elemental gases (such as medicine), the gas often accumulates in buildings. Radon accounts for around 21,000 lung cancer deaths in the US per year.
“If you imagine sorting marbles then you see the problem with sorting these atoms. They are round in shape and of a similar size, not to mention that only one marble in every million is the one you are looking for,” says lead author of a new study, Dr Andy Cooper.
Chemists and engineers from the US and the UK have used an 'organic cage molecule' called CC3 to separate krypton, radon and xenon from air at concentrations of only a few parts per million.
CC3 is a molecule made up of cavities, or cages, into which gas molecules fit very precisely.
By a process of adsorption – where molecules or atoms stick onto the surface – the right gas molecules are held in place, while others such as water or nitrogen are released.
Tests using columns of CC3 crystals have produced results far superior to previous systems, and raised the possibility that CC3 could be used for commercial processes.
It could rapidly improve the clean-up of nuclear waste or in the adsorption and detection of radon and other poisonous elements in homes.
Further studies show that CC3 also has potential in the pharmaceutical industry, which uses molecules as feedstocks in the production of drugs, and where these molecular feedstocks need to be separated from other closely related molecules.
“This material could solve commercial problems associated with the extraction of rare gases or other molecules from very dilute mixtures. The key is to design exactly the right fit between the cavity and the molecule that you want to capture,” Professor Cooper said.