Clean water is all around us, and more literally than you might think – it's floating around in the air most of the time. Of course, it’s not particularly drinkable in that form, but now researchers at the Johns Hopkins Applied Physics Lab (APL) have found materials that can collect huge amounts of water from the air.
As is the case with similar systems we've covered previously, the key lies with a material called a metal-organic framework (MOF). These structures have the highest surface area of any known material – in fact, if you were able to unfold just one gram of an MOF, it would be enough to cover a football field. And all that internal space makes them perfect for capturing and storing water.
Plenty of previous studies have managed to use MOFs to absorb water vapor from the air and collect it in liquid form for drinking. Results have varied, from 100 ml of water per kilogram of MOF used with a UC Berkeley design in 2018, to over 1.3 L (0.3 gallons) per day per kg. But the new system smashes this record.
“We identified a MOF that could produce 8.66 liters (2.3 gall) of water per day per kilogram of MOF under ideal conditions, an extraordinary finding,” says Zhiyong Xia, co-lead author of the study. “This will help us deepen our understanding of these materials and guide the discovery of next-generation water-harvesting methods.”
To create this better-performing new version, the team studied 10 different types of MOFs, examining which properties made them more effective. They also investigated how different environmental conditions, such as temperature and humidity, affected their ability to absorb water vapor.
The team plans to continue looking into other types of MOFs and how they could be combined and configured, to see if this system could work more efficiently, and perhaps in drier conditions. After all, that's where potable water is most desperately needed.
The research was published in the journal Scientific Reports. The team describes the work in the video below.
