Experts use sunlight to capture carbon

Capturing and storing carbon dioxide is essential to slow global warming, but current methods are costly and so energy-hungry they often rely on fossil fuels themselves. Now, a research team has devised a new carbon capture technique that harnesses an abundant, clean, and free energy source: sunlight.

In a recent study by Cornell University, researchers describe how they mimicked the carbon-fixing mechanism used by plants to develop the first light-powered system that can both capture and release carbon dioxide.

The method promises to lower costs and emissions associated with carbon capture, offering a sustainable alternative to existing technologies by harnessing sunlight.

A different approach to carbon capture

Carbon dioxide is notoriously difficult to trap because of its chemical stability. Most carbon capture efforts rely on amines – organic compounds derived from ammonia – that selectively bind CO₂.

However, these compounds degrade in the presence of oxygen and require constant replacement, leading to high energy costs for their production.

“From the beginning, our lab has tried to think about how we can use our intuition as chemists to find alternative pathways to carbon dioxide capture,” said senior author Phillip Milner, an associate professor of chemistry and chemical biology in the College of Arts and Sciences. “We basically have a motto of ‘anything but amines.’”

The new method relies on a stable enol molecule that becomes reactive enough under sunlight to “grab” carbon dioxide. Once captured, a shift in pH triggers the release of the CO₂ through a process known as decarboxylation.

Importantly, the entire system operates without the need for cooling between capture and release – one of the major energy bottlenecks in existing methods.

Carbon capture inspired by photosynthesis

The reaction mechanism is inspired by the enzyme RuBisCo, which plants use to fix carbon during photosynthesis. Graduate student Bayu Ahmad, who is the first author of the study, developed the concept of using sunlight to drive both carbon capture and release.

“From a chemistry standpoint, this is totally different from what anybody else is doing in carbon capture,” Milner said. “The whole mechanism was Bayu’s idea, and when he originally showed it to me, I thought it would never work. It totally works.”

The team employed 2-methylbenzophenone, a low-cost sorbent, to anchor the process. Testing revealed that the new sunlight method’s carbon capture rate matched or outperformed other light-driven technologies, while avoiding common pitfalls like the need for extensive cooling infrastructure.

Real-world testing with flue gas

Lab successes often falter when faced with real-world samples full of impurities. To address this, the researchers tested their system using flue gas from Cornell’s Combined Heat and Power Building, which burns natural gas to supply campus energy. The method successfully isolated carbon dioxide from these complex samples.

“Getting real flue gas from industry is really difficult, because companies don’t want people to know what’s coming out of their power plants,” Milner said.

“But Cornell is not a company – so this is something unique that we can offer and that we hope will be operational in the next year.”

From lab bench to solar fields

Looking ahead, the team envisions scaling the technology into installations resembling solar panels. But instead of generating electricity, these panels would extract CO₂ directly from the air, producing pure, high-pressure carbon dioxide that could be stored or converted on-site.

“We’d really like to get to the point where we can remove carbon dioxide from air, because I think that’s the most practical,” Milner said.

“You can imagine going into the desert, you put up these panels that are sucking carbon dioxide out of the air and turning it into pure high-pressure carbon dioxide. We could then put it in a pipeline or convert it into something on-site.”

Broadening the impact: Light-driven separations

The benefits of this innovation extend beyond carbon dioxide. Milner’s lab is also investigating how sunlight-powered separations could be applied to other industrial gases.

“There’s a lot of opportunity to reduce energy consumption by using light to drive these separations instead of electricity,” Milner said.

This is crucial because separation processes account for about 15% of global energy consumption. Light-powered alternatives could significantly cut those figures, aligning with global sustainability goals.

An open-source flue gas facility

In a further effort to support carbon capture research, Milner is part of a project to make flue gas from Cornell’s power plant available to other scientists and startups. This initiative, funded by the Cornell Atkinson Center for Sustainability, aims to create a unique testing ground for real-world carbon capture technologies.

By combining plant-inspired chemistry with the clean energy of sunlight, Milner and his team have opened a promising new path toward cost-effective, scalable carbon capture.

The new approach not only addresses the energy pitfalls of current systems but also offers a blueprint for sustainable industrial separations, moving closer to practical solutions in the fight against climate change.

The study is published in the journal Chem.

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