Moisture Powered Materials Could Make Cleaning CO₂ From Air More Efficient

Over the past century, the amount of carbon dioxide in the atmosphere has increased dramatically. This rise has contributed to global warming and led to many harmful effects, including shifting weather patterns and more frequent droughts. There is an urgent need to lower the amount of carbon dioxide in the air to protect ecosystems and reduce future damage to the planet.

Paul V. Galvin professor Petra Fromme in ASU’s School of Molecular Sciences (SMS), and her team, have taken an important step toward improving technologies that pull carbon dioxide directly from the air, an approach considered essential for tackling climate change. The team closely examined two promising materials that can capture CO₂ using changes in humidity, a low-energy process known as moisture-swing direct air capture (DAC). Fromme is also Director of the Biodesign Institute’s Center for Applied Structural Discovery.

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The team includes Gayathri Yogaganeshan, Raimund Fromme and Michele Zacks from SMS, Rui Zhang from ASU’s Eyring Materials Center, Jennifer Wade and Golnaz Najaf Tomaraei from Northern Arizona University’s Steve Sanghi College of Engineering, Sharang Sharang from Tescan USA Inc., Warrendale, Pennsylvania, Douglas Yates from the Singh Center for Nanotechnology, University of Pennsylvania, Philadelphia, Pennsylvania, Marlene Velazco Medel from the Center for Negative Carbon Emissions, ASU, Martin Uher from Tescan Group a.s., Brno, Czech Republic and Justin Flory from the Walton Center for Planetary Health, ASU.

“This work is so important as it shows for the first time the structural characterization of two direct air capture materials with a unique combination of techniques ranging from X-ray diffraction to electron microscopy and atomic force microscopy which we combined with functional studies on the moisture swing mechanisms of carbon dioxide binding and release,” explains Fromme.

Gayathri Yogaganeshan, Fromme’s doctoral student, is first author on the paper just published in Materials Today Chemistry.

"Our research addresses the urgent challenge of removing carbon dioxide from the atmosphere by investigating materials for low-energy, moisture-driven direct air capture,” says Yogaganeshan .

Many carbon reduction methods focused on remediation have been explored. These include reforestation, agricultural and soil management, C-biomineralization, ocean fertilization, and bioenergy generation with carbon capture and storage (BECCS). Direct Air Capture, together with permanent storage, is a promising alternative method that captures carbon dioxide directly from the air.

This study looks at two commercially available polymers, Fumasep FAA-3 and IRA-900, to see how well they work for a low-energy carbon capture method called moisture-driven direct air capture (DAC). The goal was to understand how the structure of these materials affects how they adsorb and release carbon dioxide (CO₂).

Researchers used several imaging and X-ray techniques to examine the materials’ structures at different scales. They also ran experiments that measured how much CO₂ and water the materials adsorbed and released under different humidity levels.

The results showed that both materials behave similarly when adsorbing and releasing water, suggesting that water movement is controlled mainly by their molecular structure. However, their ability to capture CO₂ differed. The material with larger pores, IRA-900, captured more CO₂ and did so more quickly. Additional imaging revealed features like pores, clustering, and swelling that help explain these differences.

Overall, the study provides insight into how these materials work during CO₂ capture and highlights the important role of moisture. This knowledge could help researchers design more energy-efficient materials for carbon capture in the future.

“Using advanced structural characterization techniques including X-ray diffraction, SAXS/WAXS, atomic force microscopy, FIB-SEM, and TEM, combined with moisture-swing sorption experiments, we linked molecular-scale ordering, pore architecture, and hydration dynamics to CO₂ uptake and release,” explains Yogaganeshan.

“We found that hydration dynamics are controlled primarily by molecular structure, while CO₂ sorption kinetics and capacity are strongly influenced by macropore architecture and charge site density, with more open structures exhibiting enhanced uptake and faster initial kinetics. Surface analyses confirmed clustering, porosity, and swelling, revealing how subtle structural features govern performance. These insights provide a foundation for designing more energy-efficient materials for scalable carbon dioxide removal, with implications for advancing practical carbon capture technologies.”