An international team of scientists are using porous sponge-like materials that can trap carbon dioxide in their cavities while letting other gases such as nitrogen through.
The materials are made from sugar and low-cost alkali metal salts, so they would be cheap enough for large-scale deployment, and they could be particularly effective in limiting environmental damage from coal-fired power plants.
The team’s article is published in applied chemistry, a publication of the German Chemical Society. Phillip Milner, assistant professor of chemical and chemical biology at Cornell University, led the collaboration.
For the past 100 years, the primary method of capturing carbon in chemistry has been a process known as amine washing. Amines are organic compounds derived from ammonia that contain nitrogen. In aqueous solution, they are able to selectively remove carbon dioxide from gas mixtures. However, oxygen degrades them every time they are cycled, meaning more and more material would have to be produced, driving up the cost.
Rather than trying to figure out how to overcome the amine oxidation problem, Milner’s lab experimented with a different family of materials and designed them specifically for carbon dioxide capture.
The new project focuses on sponge-like materials containing hydroxide sites in their pores. As a rule, solutions of hydroxide salts react reversibly with carbon dioxide and form bicarbonate salts, such as baking soda, trapping carbon dioxide. But to regenerate the hydroxide salt, the material needs to be heated up to 500 to 800 degrees Celsius, which is no small feat, and not cheap either.
Lead author and doctoral student Mary Zick found that by incorporating bundles of sugar molecules called cyclodextrins as a starter and boiling them with alkali metal salts in water, she could create a sponge-like material that is riddled with cavities in which carbon dioxide binds strongly, but into which other gases such as nitrogen easily pass.
“Coal emissions are still the number one anthropogenic contributor to carbon dioxide emissions globally,” Milner said. “What’s great about this work is that Mary not only found a useful material for capturing carbon dioxide from coal flue gases, but she also described the structure-property relationships that will allow us design materials for other applications, such as CO capture2 natural gas power plants, as well as maybe even air, which is one of the very big challenges of our time.”
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Mary E. Zick et al, Carbon dioxide capture at nucleophilic hydroxide sites in oxidation-resistant cyclodextrin-based metal organic frameworks, International Edition of Applied Chemistry (2022). DOI: 10.1002/anie.202206718
Provided by Cornell University
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