Campus researchers improve conversion of carbon dioxide into useful products

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A group of UC Berkeley researchers has found ways to better reduce carbon dioxide into carbon monoxide in order to make chemical products, such as fuel and plastics.

The group, led by campus chemistry professors Christopher Chang and Omar Yaghi, published a study earlier this month in which the team explained how incorporating catalysts into crystals allows them to convert carbon dioxide into carbon monoxide more efficiently. Using these sponge-like crystals — which exist in covalent organic frameworks and are visible to the naked eye as a fine, brown or reddish powder — is one of the most efficient ways to reduce carbon dioxide into carbon monoxide.

“The conversion is a big deal since it opens a new route to making interesting materials,” said campus chemistry and earth and planetary sciences professor Ronald Cohen. “That is an important accomplishment, independent of whether it leads to ideas for addressing the greenhouse gas issue.”

Carbon-capturing materials are already being explored by scientists to improve solutions related to greenhouse gases in the atmosphere, and similar materials are in development at UC Berkeley. The Lawrence Berkeley National Laboratory research group published its August paper in Science with lead authors Song Lin, Christian Diercks and Yue-Biao Zhang.

“We have a choice of burying carbon dioxide at a cost of about $50 per ton (with) current technology … or recycling carbon dioxide into fuels,” Cohen said in an email. “If the cost of converting to fuels becomes low enough, then this idea would be important to controlling climate change.”

The crystals’ structure has a very high internal surface area like a sponge, allowing them to absorb larger amounts of carbon dioxide than ever before.

Carbon monoxide can already be turned into fuel using several processes. One such technology, known as the Fischer-Tropsch process, has been employed on a large scale in South Africa.

The group sought to make the process cheaper and more efficient than previous experiments. The team used cobalt, a naturally abundant and relatively inexpensive material that makes the process more environmentally friendly. The reaction is also done in water instead of “environmentally questionable” organic solvents, Diercks said.

“There have been many attempts to develop homogeneous or heterogeneous catalysts for carbon dioxide, but the beauty of using (these frameworks) is that we can mix-and-match the best of both worlds,” Chang said in a press release.

The catalysts, which are organic molecules containing cobalt, are suspended in the porous structure, preventing them from contacting one another and deactivating.

Researchers can also manipulate the structure of the framework to better understand how it influences the chemical reaction, Diercks said.

Diercks said the material could potentially work in power plants to absorb carbon dioxide and convert it into carbon monoxide.

The researchers are still working with milligrams of material, according to Diercks, but they plan to optimize the material to be able to make large quantities at low costs. The team has already shown the initial results of optimizing the amount of cobalt in the catalysts and will continue to focus on making the process more efficient.

Contact Madeleine Pauker at [email protected] and follow her on Twitter at @powkur.