A group of researchers from the School of Engineering at the University of California at Viterbi aims to split CO2 and convert this greenhouse gas into useful materials like fuels or consumer goods, from pharmaceuticals to polymers. The research results are published by the Journal of Physical Chemistry A.

Typically, this CO2 separation process is energy-intensive. However, in the first computational study of this kind by Shaam Sharad, WISE Gabilan associate professor and her team decided to use the Sun as an assistant in this process.

In particular, they demonstrated that ultraviolet light can be very effective in exciting the organic oligophenylene molecule. When exposed to UV light, oligophenylene becomes a negatively charged anion, easily transferring electrons to a nearby molecule such as CO2. Thus, carbon dioxide becomes able to recover and turn into an integral part of plastics, medicines, or even furniture.

“CO2 is notoriously difficult to reduce, so it lives in the atmosphere for decades. But this negatively charged anion is capable of reducing even such a stable product as CO2, so it is promising and therefore we are studying it”.

Shaam Sharada, Associate Professor WISE Gabilan

The rapidly increasing concentration of carbon dioxide in the Earth’s atmosphere is one of the most pressing problems that humanity must solve in order to avoid a climate catastrophe.

Since the beginning of the industrial era, humans have increased their atmospheric CO2 emissions by 45% through the burning of fossil fuels and other emissions. As a result, average global temperatures are now two degrees Celsius higher than in the pre-industrial era. Thanks to greenhouse gases like CO2, solar heat stays in the atmosphere, heating our planet.

Many research groups are exploring methods for converting CO2 captured by emissions into fuels or carbon feedstocks for consumer products, from pharmaceuticals to polymers.

The process traditionally uses heat or electricity along with a catalyst to accelerate the conversion of CO2 into products. However, many of these methods are often energy-intensive, which is not ideal for a process to reduce environmental impact. Using sunlight to excite a catalyst molecule is in turn energy efficient.

“Most other ways to do this involve the use of metal-based chemicals, and these metals are rare earth metals,” said Sharada. “They can be expensive, difficult to find, and potentially toxic.”

This work was the first computational study of its kind, as scientists had not previously studied the basic mechanism for the movement of an electron from an organic molecule such as oligophenylene to CO2. The team found they could systematically modify the oligophenylene catalyst by adding groups of atoms that confer specific properties when bound to molecules that tend to push electrons towards the center of the catalyst to speed up the reaction.

The team is now exploring catalyst design strategies that not only result in high reaction rates but also allow the excitation of a molecule with visible light, using both quantum chemistry and genetic algorithms.