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Published: 18 March 2013

On the road to a gas-powered future

Microporous storage materials being developed by researchers in the Department of Chemical and Process Engineering are steering motorists towards a cleaner future…

A significant breakthrough in the way fuel is stored in cars could make it possible for vehicles to store enough hydrogen or methane to travel long distances, bringing the dream of mass-produced gas-powered cars one step closer.

Revolutionary materials known as metal-organic frameworks (MOFs) are being developed to enable vast quantities of gas to be stored in molecular structures. Dr Ozgur Yazaydin from the Department of Chemical and Process Engineering and his colleagues at Northwestern University in the US, have found a way to squeeze huge quantities of hydrogen or methane into a single gram.

If the internal surface areas of the new MOF materials produced by the team were unfolded, they would occupy an area equivalent to the Emirates Stadium, where Arsenal plays its home games in the Premier League.

The drive for cleaner vehicles has intensified interest in the potential fuel storage applications of MOFs in recent years. For gas-fuelled cars to be a viable future transport option they need to be able to carry sufficient fuel for a journey. It had previously been thought that limits on storage capacity would make widespread usage of these cleaner vehicles a practical impossibility.

So how do MOFs work? Metal atoms are connected by organic linker molecules to create a network of molecular cages with vast internal surface areas – ideal for storing gases. The greater the surface area, the more hydrogen or methane can be stored, and the further the car is able to travel.

Dr Ozgur Yazaydin and his colleagues have demonstrated that it is possible to develop surface areas in MOF materials that are around 40% greater than those produced in previous studies.

The question is: how are such huge storage capacities unlocked? “The key is exposing more surface area relative to the available space for gas molecules to stick,” says Dr Yazaydin, who led the theoretical part of the study.

“Benzene molecules, commonly used in MOFs as organic linkers, are like hexagonal rings. Gas molecules can only stick to the ring’s outer surface, so the inner sides of each benzene unit are essentially wasted space. If you break the ring and straighten it, both sides become available for gas adsorption. That is exactly what we’ve done. The breakthrough heralds a whole new dimension to the potential use of gas for powering vehicles.”

Find out more

Read more about Dr Yazaydin’s work in the August 2012 issue of the Journal of the American Chemical Society

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