Microporous material could store gas as fuel in cars

5 October 2012

A team from the Department of Chemical Engineering at Surrey University alongside collaborators at Northwestern University in the US recently validated their new metal-organic framework (MOF) configuration.

‘The breakthrough heralds a whole new dimension to the potential for using gas to power vehicles,’ said study lead Dr Ozgur Yazaydin of Surrey.

In recent years, there has been considerable interest in MOFs, which are microporous crystalline materials where metal atoms are connected by organic linker molecules. This results in a network of molecular cages with vast internal surface areas ideal for storing gases.

Cars fuelled by these gases, either through conventional combustion engines or fuel cells, must however be able to carry enough gas to achieve a range that is viable and competitive with gasoline or electric vehicles.

Based on the way the gas is stored using MOFs, scientists had previously assumed there was theoretical finite limit to capacity, making the idea impractical.

However, employing some novel modifications the current team has demonstrated that it is possible to achieve around 40 per cent higher surface areas in MOF materials than previously demonstrated, from a Brunauer-Emmett-Teller (BET) surface area of around 7,000m²/g to 14,600m²/g.

‘The key is exposing more surface per available space for gas molecules to stick,’ said Yazaydin. ‘Benzene molecules, which are commonly used in MOFs as organic linkers, are like hexagonal rings, and gas molecules can only stick onto the ring’s outer surface, thus the inner sides of each benzene unit are essentially wasted space. If you break the ring and straighten it, then both sides become available for gas adsorption. That is exactly what we did.’