Carbon dioxide can be a chemical building block.

Synopsis by Evan Beach, Mar 17, 2011

Beckman, EJ, and P Munshi. 2011. Ambient carboxylation on a supported reversible CO2 carrier: ketone to b-keto ester. Green Chemistry http://dx/doi.org/10.1039/c0gc00704h.

Laboratory trials of a coated silicone material may pave the way for the use and reuse of carbon dioxide in the chemical industry. Carbon dioxide can be used as a raw material for ingredients found in pharmaceuticals, pesticides and other specialty chemical products. The landmark process is explained in a recent article in the journal Green Chemistry.

The discovery won’t significantly impact global carbon dioxide emissions, but it will make it easier for chemists to work with an inexpensive, abundant source of carbon that’s widely available as a waste material.

Carbon dioxide has been widely used in the preparation of larger molecules, but the need for high pressure to make the reactions go is a major limitation. The scientists found that by using a specially designed carrier material, carbon dioxide can be used at room pressure.

The carrier material is based on silicone with a permanent chemical coating that absorbs the carbon dioxide. The carbon dioxide binds at room temperature, but is only released if the material is heated to 120 degrees Celsius (about 250 F). These properties allow the bound carbon dioxide to be used within a wide range of temperatures.

The material can be easily separated from reaction mixtures, making it easy to purify the chemical products. This represents a major improvement over liquid-based carbon dioxide absorbents, which require extra steps to separate. The solid carrier is also easily recycled: the researchers saw no loss of activity after five cycles of carbon dioxide binding and release.

The material was tested for its ability to promote chemical reactions that add carbon dioxide to other molecules. Good efficiency was found at room temperature and pressure. No silicon was found in the chemical products, indicating that the carrier material is very stable.

The researchers also showed the carrier material could improve the reactivity of other molecules besides carbon dioxide, so it could be more widely useful. Future work might explore a wider variety of carbon dioxide chemistry, including manufacturing of plastics.