Australasian Science: Australia's authority on science since 1938

Carbon Capture Stimulated by UV Light

By Stephen Luntz

If the coal industry has a future in a carbon-constrained world, its saviour may be a form of solar power.

Billions of dollars have been poured into carbon capture and storage as a way to prevent the carbon dioxide produced while burning fossil fuels from reaching the atmosphere. However, one of the greatest obstacles has been the fact that the amines on which research has focused require 20% of the energy produced by the power station just to release the captured carbon for storage, putting a floor under the possible price.

Dr Matthew Hill of CSIRO Materials Science and Engineering has found a way around this challenge. He is using metal organic frameworks (MOFs) to capture gases.

The MOFs are too expensive to simply store the carbon they collect. Instead, like the amines, they capture it from the exhaust chimney of the power station and release the carbon dioxide in a purer form later so it can be transported and stored while the MOF is reused.

While previous products needed large amounts of heat energy to release the carbon, Hill is achieving the same effect with sunlight. “The capture and release process can be compared to soaking up water with a sponge and then wringing it out,” says Hill. “When UV light hits the material, its structure bends and twists and stored gas is released.”

The effect is achieved by doping the MOF with light-responsive azobenzene molecules that respond to UV light.

In the journal Angewandte Chemie Hill reported the production of a MOF that releases 64% of the absorbed carbon as soon as it is exposed to sunlight. The MOF also does an excellent job of instantaneously absorbing gas as it flows past, so the waste does not need storage.

But Hill’s MOFs are far from ready to attach to power stations. For one thing there is the problem of exposing large areas of lattice to light. “This is very difficult,” Hill says.

“What we have done is really a proof-of-concept. We used UV light but are looking at other types of light that will penetrate solid material and have the same effect.”

Coal-fired power stations release many other pollutants, and Hill imagines these will be “removed at a prior step” before the larger problem of carbon dioxide is tackled so that the MOFs do not degrade.