A new way to capture water — from air and with sunlight

UI chemists design a light-triggered structure that could alleviate global water scarcity

Friday, May 8, 2026

Chemists at the University of Iowa have created a three-dimensional lattice that captures water from the air and stores it.

In a new study, researchers describe a millimeter-scale structure made of metal atoms connected by two types of organic molecules. When exposed to ultraviolet light, the material undergoes a chemical reaction that changes its shape, creating cavities throughout the lattice. Those cavities attract water molecules from the air and store them - like a multitude of tiny canteens.

The results, which would need to be tested at larger scales, show promise as a method to help provide drinking water to people and areas with limited access. Water stress or scarcity will affect nearly 5 billion people - half the world's projected population - by 2050, according to the United Nations.

"We have found and validated a way to capture and to store water that would require only sunlight," says Leonard MacGillivray, adjunct professor in the Department of Chemistry and former professor and department chair. "You can transport the crystal lattice and eventually release the water on demand. That's why it's such an advance."

MacGillivray's group discovered the water-capturing architecture while tinkering with metal-organic frameworks (MOFs), which combine metal atoms and organic linkers to form 3D structures with pore-like openings. The technique, developed in the 1990s, earned its pioneers the 2025 Nobel Prize in chemistry.

The Iowa team's initial attempts at creating MOFs yielded no cavities.

"Our design had linkers, which should give us pores, but flexibility we had built into the linkers did not allow for cavities to form," says Nevindee Samararathne Muhandiramge, a graduate student in MacGillivray's lab and the study's first author.

But when the researchers exposed the structure to ultraviolet light, cavities formed inside the crystals - with an additional surprise.

"Lo and behold, when we looked at the internal structure of the crystal using X-ray diffraction, we found water inside," MacGillivray says.

Chemists led by the University of Iowa have created a three-dimensional structure that captures water from the air and stores it. The box-like illustration in the center shows the structure before (left side) and after undergoing a chemical reaction involving sunlight (flames in center). The resulting lattice (right side) includes cavities that capture and store water molecules. The diagrams in the upper left and lower right show the chemical arrangement before and after the light-induced reaction. (Illustration credit: Nevindee Samararathne and Leonard MacGillivray group at University of Iowa/Universite de Sherbrooke, Canada, Tamador Alkhidir and Sharmarke Mohamed group at Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates)

The UV light-induced chemical reaction is the key element to the water-capturing lattice. Linkers within the framework, which loosely resemble pairs of parallel lines in the letter "H," rearrange into an X-shaped pattern when exposed to light. In three dimensions, this creates numerous cavities, each capable of capturing and storing two water molecules, which equates to 5% of the filled structure's mass.

"We do not know exactly how the water molecules travel into the crystal, but they're probably hydrogen bonding on the surface to some extent," MacGillivray says. "When the light hits the crystal, all these cavities start to pop open, water migrates in, then finds a resting place in the cavities."

Although each cavity stores a small amount of water, scale could make the approach impactful, the chemists note. These chain-like configurations can, in principle, be produced nearly endlessly.

"They assemble themselves for us," says MacGillivray, who is Canada Excellence Research Chair at the University of Sherbrooke in Quebec. "There are countless numbers, so this is a good start."

The researchers say the method could "advance developments in intelligent water harvesting technologies."

"The reason why we use the word 'intelligent' is because we're triggering the water capture intentionally with the light," Samararathne Muhandiramge says. "UV light is freely available from the sun. So, the next step would be to determine the limits of the water uptake in terms of mass percent and push that limit as far as we can."

The researchers used cadmium atoms as a proof of concept and are investigating less toxic alternatives.

The study, "Photo capture of water by single crystals of a nonporous metal−organic material," was published online March 30 in the Journal of the American Chemical Society.

Study authors include Davide Proserpio of the Università degli Studi di Milano, in Italy; Eric Reinheimer of Rigaku Americas Corporation in The Woodlands, Texas; Farshid Effaty of the University of Sherbrooke; and Tamador Alkhidir and Sharmarke Mohamed of Khalifa University of Science and Technology in Abu Dhabi, United Arab Emirates.

The U.S. National Science Foundation funded the research.

Analyses using X-ray diffraction and thermal techniques were performed at the Materials Analysis, Testing, and Fabrication Facility, created at Iowa in 2019 by the Office of the Vice President for Research to advance micro-nanofabrication research.