Converting CO2 Into Useful Materials Using Sunlight

We know that carbon dioxide is one of the major reasons for global warming and the problem is that it is a very stable molecule and needs a lot of energy for its breakdown. But recent research aims to solve this problem.

In the first computational study of its kind, a team of researchers from Viterbi School of Engineering, University of South California had shown that we can break CO₂ apart and convert the greenhouse gas into useful materials like fuels or consumer products ranging from pharmaceuticals to polymers. Moreover, this can be achieved with a sustainable energy source – the Sun.

The team from Mork Family Department of Chemical Engineering and Materials Science was led by third year Ph.D. student Kareesa Kron. Their work appeared recently in Journal of Physical Chemistry A

Basically, the team demonstrated that ultraviolet (UV) light could be very effective in exciting an organic molecule called oligophenylene. Upon exposure to UV, oligophenylene becomes a negatively charged “anion,” readily transferring electrons to the nearest molecule, such as CO₂ — thereby making the CO₂ reactive and able to be reduced and converted into things like plastics, drugs, or even furniture.

“CO₂ is notoriously hard to reduce, which is why it lives for decades in the atmosphere,” said Shaama Sharada, a WISE Gabilan Assistant Professor and the supervisor of the research. “But this negatively charged anion is capable of reducing even something as stable as CO₂, which is why it’s promising and why we are studying it.”

Some previous processes to break CO₂ typically used either heat or electricity to excite catalysts which is energy-intensive which won’t help us reduce environmental impact. Using sunlight instead is obviously an attract

Most other methods involve using metal-based chemicals, and those metals are rare earth metals which can be too expensive and toxic as well.

Though the current method seems better it holds its problems which the team aims to address. The team uses quantum chemistry simulations to understand how electrons move between the catalyst and CO₂ to identify the most viable catalysts for this reaction.

According to researchers, this work is the first computational study of its kind wherein researchers had not previously examined the underlying mechanism of moving an electron from an organic molecule like oligophenylene to CO₂. The team found that they can carry out systematic modifications to the oligophenylene catalyst, by adding groups of atoms that impart specific properties when bonded to molecules, that tend to push electrons towards the center of the catalyst, to speed up the reaction

“One of those challenges is that, yes, they can harness radiation, but very little of it is in the visible region, where you can shine light on it in order for the reaction to occur,” said Sharada. “Typically, you need a UV lamp to make it happen.”

The team is now trying to figure out catalysts that not only lead to high reaction rates but also allow for the molecule to be excited by visible light.

Journal Reference:
Kareesa J. Kron, Samantha J. Gomez, Yuezhi Mao, Robert J. Cave, Shaama Mallikarjun Sharada. Computational Analysis of Electron Transfer Kinetics for CO2 Reduction with Organic Photoredox Catalysts. The Journal of Physical Chemistry A, 2020; 124 (26): 5359 DOI: 10.1021/acs.jpca.0c03065