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CSIRO’s got gas

By Pat, 13 September 2012 News

Electron micrograph of a metal organic framework

Metal organic frameworks could reduce greenhouse gas emissions.
Image: CSIRO/Paolo Falcaro and Dario Busa

It’s Australian footy finals season, and millions of eyes around the country are focused on the football field. Now imagine the area of that football field and fold it in half. Keep folding and folding until it’s small enough to sit in a spoon. Sounds impossible, right?

Actually, there are materials that contain a football field’s area in just one gram. They’re called MOFs and their gas storage abilities recently won CSIRO scientist Dr Matthew Hill a Eureka Prize.

MOF stands for metal organic framework. ‘Metal’ refers to the fact that these materials contain metal ions. MOFs usually contain relatively light metal ions, such as copper, calcium or magnesium.

What holds these metal ions together? That’s where the ‘organic’ part comes in. Organic chemicals are a huge class of compounds based on the elements carbon and hydrogen. In MOFs, the metals are linked together by organic molecules.

The metal ions and organic molecules are arranged to create a ‘framework’. The structure of the material is such that it has a huge surface area in a small mass.

Think of scaffolding around a building. The surface area of the building is the combined area of its walls. The scaffolding, however, is made of struts, poles and platforms, which have a relatively large area. The scaffolding also has a large surface area inside its structure.

So while the building has a much larger mass, the scaffolding weighs less with a higher surface area. MOFs are like the scaffolding – they form a structure that has low mass, but high surface area.

MOFs have an important property: they can adsorb large volumes of gas. This is because the gas molecules can fit easily into the holes and gaps within the MOF structure. CSIRO is currently researching the use of MOFs to capture gases. Such research is an important part of broader research into reducing greenhouse gas emissions.

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