Researchers Harness Light-Reactive Molecules to Capture Carbon Dioxide

In the battle against global warming, a team of researchers at ETH Zurich has devised a groundbreaking carbon capture process that utilizes the power of light. This innovative method not only provides a more sustainable approach to combating climate change but also holds significant implications for the future of our planet.

The new technique developed by the team involves directing air through a liquid to capture carbon dioxide (CO2). When exposed to light, the captured greenhouse gas is released and can be collected.

In a departure from traditional carbon capture technologies that rely on temperature or pressure differentials, requiring substantial energy consumption, this novel light-based process avoids such energy-intensive requirements. The researchers at ETH Zurich leveraged the fact that CO2 exists in its gaseous form in acidic aqueous solutions, while in alkaline aqueous solutions, it undergoes a reaction to form carbonates, known as salts of carbonic acid. This reversible chemical transformation is governed by the acidity level of the liquid.

To control the acidity of their liquid, the scientists introduced photoacids—molecules that react to light. When exposed to light, these molecules induce acidity, and in the absence of light, they revert to their original state, rendering the liquid more alkaline. The process begins by guiding air through a light-deprived liquid enriched with photoacids, causing CO2 to react and form carbonates. Upon light exposure, the acidity prompts the conversion of carbonates back into CO2, releasing it from the liquid, akin to bubbles in a cola bottle. Once CO2 levels in the liquid are minimized, the researchers deactivate the light source, restarting the cyclic process for further CO2 capture.

While conducting practical experiments, the team encountered a challenge as the photoacids used proved unstable in water, decomposing within a day. To address this, they shifted the reaction to a blend of water and organic solvent. Through lab experiments and model calculations by researchers from Sorbonne University, they optimized the liquid ratio, stabilizing the photoacid molecules for nearly a month and facilitating reversible switching between acidity and alkalinity using light.

In comparison to other cyclical carbon capture methods, which often involve filters trapping CO2 molecules at ambient temperature, this new approach offers a quicker switch between carbon capture and release. Anna de Vries, a doctoral student in Lukatskaya's group and lead author of the study, noted, "Another fascinating aspect of our system is its ability to shift from alkaline The system has an interesting feature – it can change from acidic within seconds to alkaline within minutes. This allows us to switch between capturing and releasing carbon much more swiftly compared to a system driven by temperature."

Looking ahead, researchers aim to enhance the stability of photoacid molecules while exploring comprehensive process parameters for further optimization.