An ultraporous humidity sponge could provide 300 gallons of fresh water a day
An ultraporous compound can extract water molecules from dry desert air, store them as tiny "Icicles" and then release them as clean drinking water.
Along with government, industry and university partners, the researchers are working to turn their project into portable hydration systems capable of conjuring fresh water almost anywhere in an increasingly thirsty world.
Yaghi's team had previously developed MOF-303 specifically for water extraction and successfully demonstrated it in dry laboratory conditions and an Arizonan desert.
The experimental results matched theoretical predictions the researchers had made about MOF-303's behavior: The material's nanoscale pockets readily fill up with water vapor because the internal pore walls are "Decorated" with sites that attract water molecules, Yaghi says.
These captured molecules rapidly form hydrogen bonds with other passing water molecules, seeding what Yaghi describes as dense, ambient-temperature ice crystals.
Although they remain at air temperature, the molecules join together like they do in ice, filling the pores with solid water structures.
"First the water molecules form isolated clusters, then chains of clusters, and finally a water network carpets the interior space," he explains.
Once the MOF has filled its pores with these minuscule icicles, applying a little extra heat is enough to release the molecules as potable drinking water.
The new MOF-303 study is supported by the U.S. Defense Advanced Research Projects Agency's Atmospheric Water Extraction program: a four-year research-and-development effort that aims to reduce the risks and logistic costs of transporting water supplies to troops in the field.
"If you're loading up the front sites first, as water molecules flow into the pocket, it can impede full uptake." The process is a little like boarding an airliner: If everyone grabs the first seats up front, that slows access to the rear seats.