Scientists have come up with an innovative way to try and counter the massive amounts of carbon dioxide we're still pumping into the air, even as a climate crisis unfolds around us: turning that CO2 into a useful organic polymer.
The newly developed method sucks CO2 molecules out of the air, without expending much energy in the process. The material can then potentially be turned into an ingredient for packaging or clothing.
The secret weapon is a porous coordination polymer (PCP) made up of zinc metal ions.
Those ions are able to selectively capture CO2 molecules with 10 times greater efficiency than other PCPs, the scientists say. What's more, the material is reusable, and was still running at maximum efficiency after 10 reaction cycles.
"We have successfully designed a porous material which has a high affinity towards CO2 molecules and can quickly and effectively convert it into useful organic materials," says materials chemist Ken-ichi Otake, from Kyoto University in Japan.
The idea of carbon sequestration has been around for some time, but the low reactivity of carbon dioxide means it's difficult to capture and lock away without using a lot of energy along the way – which kind of defeats the point.
PCPs (also known as metal-organic frameworks or MOFs) might hold the key to overcoming this obstacle. The one outlined in this new study uses a clever trick: an organic component with a propeller-like structure.
Using X-ray structural analysis, the researchers found that as CO2 molecules approach the PCP, its molecular structure rotates and rearranges, allowing the carbon dioxide to be trapped in the material.
The PCP is essentially working as a molecular sieve, able to recognise molecules by size and shape. Once the material has done its CO2-sucking job, it can be reused or recycled as an organic polymer. Organic polymers are able to be turned into polyurethane, which is used in clothing, packaging, domestic appliances and a variety of other areas.
We're seeing a number of promising in the field of carbon storage. Earlier this year scientists from RMIT University in Australia presented a way of turning CO2 back into coal, using a chemical reaction involving the metal cerium.
Another team of researchers, from Rice University in the US, have been able to develop a device for turning CO2 into liquid fuel: in this case the metal bismuth is the key ingredient, and formic acid is the end result.
All these ideas require further research and need to work at larger scales, but progress is being made. That said, they shouldn't distract us from the best way of cutting down the CO2 in the air and slowing global warming – reducing our carbon emissions.
It's clear that action needs to be taken, and fast. This new CO2 conversion method may well become very important to us in the future, not least because it turns something we don't want into something we do.
"One of the greenest approaches to carbon capture is to recycle the carbon dioxide into high-value chemicals, such as cyclic carbonates which can be used in petrochemicals and pharmaceuticals," says materials chemist Susumu Kitagawa, from Kyoto University.
The research has been published in Nature Communications.