Chemists and engineers find innovative ways to access water—including by pulling it out of thin air. Now, University of Chicago researchers found a way to extract even more water.
In 2021, Prof. Laura Gagliardi of the Pritzker School of Molecular Engineering (PME) and the Department of Chemistry was part of a cross-institutional team developing a new device to extract water from air. The key innovation was a designed material called a metal-organic framework (MOF), a hybrid structure of metal ions and organic linkers that can be tuned at the molecular level.
MOFs have a structure of empty pores that adsorb water molecules from air. Gagliardi and her team used theoretical and computational methods to better understand how the material worked at the atomic level.
Now, Gagliardi’s team has helped guide the design of an optimized MOF that adsorbs 50 percent more water from the air than the previous version. The material will ultimately be incorporated into a device built to demonstrate this potentially game-changing technology.
Though the original MOF worked well, the team wanted to improve it by increasing the material’s pore volume, but at the same time keeping a similar binding strength to water. The MOF framework consists of tiny aluminum-based rods connected by “linker” molecules. This structure creates pores that are lined by alternating hydrophilic (water-binding) and hydrophobic (water-avoiding) pockets. These pockets are ideally suited for the initial binding of water—when the MOF is exposed to air, water molecules naturally bind themselves to it. Once the initial water molecules are bound, then the following molecules attach themselves to the initial water molecules.
The result is a “sponge” full of water. But the researchers wanted to increase the pore volume (which would allow space for more water to be extracted from the air) while still keeping this special environment needed to attract the initial water molecules. The team also had to find the right sweet spot in design: water needed to bind to the MOF, but not too strongly, or else it could never be desorbed (squeezed out of the sponge).