Scientists at the University of Iowa have developed a new material that can capture water directly from the air using only light.
The discovery could one day help provide drinking water in dry regions where clean water is difficult to access.
The research, published in the Journal of the American Chemical Society, describes a crystal-like material that changes shape when exposed to ultraviolet (UV) light.
As the structure shifts, tiny pockets open inside the material and trap water molecules from the surrounding air.
The scientists say the material acts almost like a giant collection of microscopic water bottles.
“We have found and validated a way to capture and to store water that would require only sunlight,” says Leonard MacGillivray, one of the researchers behind the study. “You can transport the crystal lattice and eventually release the water on demand.”
The new material belongs to a class of substances called metal-organic frameworks, or MOFs. These materials are built from metal atoms linked together by organic molecules, creating three-dimensional structures filled with tiny openings. Scientists have studied MOFs for decades because they can trap gases, chemicals, and other substances inside their pores.
At first, the Iowa research team struggled to create the cavities needed for water storage. Their design included flexible molecular linkers, but the structure stayed too compact.
Then the researchers tried exposing the material to UV light.
The result surprised them. The light triggered a chemical reaction that changed the arrangement of the molecular linkers inside the framework. The linkers, which originally resembled parallel lines, shifted into an X-like shape. This rearrangement opened many tiny cavities throughout the structure.
When the team examined the material using X-ray analysis, they discovered that water had already entered the cavities.
“Lo and behold, when we looked at the internal structure of the crystal using X-ray diffraction, we found water inside,” MacGillivray says.
Each cavity can hold two water molecules. That may sound very small, but together the stored water makes up about 5% of the material’s total mass when fully filled.
The scientists believe water molecules likely move along the surface through hydrogen bonding before settling into the newly opened spaces.
Although the current version stores only a modest amount of water, researchers say the material could potentially be produced in very large quantities because the crystal structures naturally assemble themselves.
The work is still at an early stage, and the researchers want to improve how much water the material can absorb. They also plan to replace cadmium, the metal currently used in the framework, with safer and less toxic alternatives.
The team describes the system as an “intelligent” water-harvesting technology because the water capture process can be switched on intentionally using light. Since UV light is naturally available from the sun, the approach may eventually offer a low-energy way to collect clean water from the atmosphere.
With climate change and water shortages expected to affect billions of people in the coming decades, technologies like this could become increasingly important in the future.
