University of Iowa researchers develop method of capturing water from the air

Research crystalized at the University of Iowa has created a way to capture water from the atmosphere that, if found to be scalable and confirmed as safe, could help solve problems of water scarcity in the future.

Nevindee Samararathne Muhandiramge, a UI Ph.D. student studying chemistry, and former UI professor of chemistry and pharmacy Leonard MacGillivray, have developed a three-dimensional lattice that, when exposed to ultraviolet light, expands just enough to attract and capture water molecules from the air.

Muhandiramge cited the United Nations in discussing the future of water access for the world, saying there is expected to be more than 5 billion people who will face issues of water like lack of access by 2050.

“It’s a huge global challenge, you know,” MacGillivray said. “The answers are going to come from different perspectives, and we’re excited we can contribute to this in this way, and I guess we’ll see where it goes in terms of the future.”

While the tiny, cube-shaped crystal lattice can only capture two water molecules per pocket, with a capacity totaling 5% of its total mass, Muhandiramge and MacGillivray said they’re trying to “generalize” their findings with the eventual goal of making the crystal-creation process more efficient and figuring out how to release the water once it is captured.

The team’s work, published in the “Journal of the American Chemical Society” at the end of March, was funded with a three-year, $500,000 grant from the National Science Foundation. Researchers from Texas, Canada, Italy, and the United Arab Emirates were also involved in the study.

Work by MacGillivray, now a research chair at the Université de Sherbrooke in Quebec, and Muhandiramge is in the field of crystal engineering, he said, and the grant was for them to study chemical reactions in crystals they’ve made out of metal atoms and organic molecule connectors.

Using water as a solvent, MacGillivray said the team mixed the lattice’s components in the solvent and heated it all up in a closed vessel over multiple days, which leaves them with enough produced crystal to work with.

While they were successful in creating the framework for the crystal with the metal and linkers, MacGillivray said the pockets and cavities they were hoping to see within the structure weren’t there. It wasn’t a given that there would be pockets, and Muhandiramge said the material was densely packed with no empty spaces inside.

However, when the team shined UV light onto the closely packed cube, it opened very slightly and created pockets.

“These small pockets …  you can think of them as a vacuum,” Muhandiramge said. “So it sucks water from the atmosphere into the material, and then stores it inside the material.”

MacGillivray said it was a big surprise to see the formed pockets, which they found using X-ray diffraction to see how atoms were arranged in the crystal. In principle, he said, researchers could further develop the crystals to intentionally bring in more water, but then they would need to figure out how to then release the water from it.

This is a scalable practice in theory, MacGillivray said, but they’re still working on “generalizing” the project results. One of the challenges of crystal engineering is that the slightest differences in components and their mixture could lead to the resulting crystal having an entirely different framework.

The goal is to figure out how to create similar frameworks to the one they have, MacGillivray said, using different linkers to hopefully get larger pockets and cavities to get more water. He and Muhandiramge are also exploring a different method of crystal creation, using grinding with less solvent than the current method.

According to the U.N., drought costs across the world exceed $307 billion annually, and by 2050, three out of four people could see impacts from drought. A 2021 UNICEF report stated more than 1.4 billion people “live in areas of high or extremely high water vulnerability.

While further tests will need to be done to determine whether the water captured through the lattice would be pure enough to drink, and further study in general needs to happen to answer their questions of scalability and generalization, MacGillivray said the work they are doing now could help other projects years down the line.

“I think studies show that 30 years from now, the kind of work we’re doing ends up finding its way into mature applications,” MacGillivray said. “So I think we need to stay ahead of the curve, basically, of environmental issues, health issues, everything that can help sustain the goodness of us all.”