image: Markus Kalmutzki, Farhad Fathieh and Eugene Kapustin set up the water harvester for tests on a rooftop on the UC Berkeley campus. The MOF is inside the interior box, and the foil-wrapped top is designed to keep the outer box cool enough to condense the water vapor driven from the MOF by sunlight. (Photo credit: Stephen McNally)
The International Union of Pure and Applied Chemistry (IUPAC) has released the results of its first search for the Top Ten Emerging Technologies in Chemistry. Initiated as a special activity in honor of IUPAC’s 100th anniversary this year, the results have been published in the 2019 April-June 2019 issue of Chemistry International. Research from the lab of Omar Yaghi at UC Berkeley on water harvesting from desert air technology has been featured as one of the top 10.
According to the United Nations (UN), water scarcity affects more than 40% of the global population and is projected to rise. On top of that, three in ten people lack access to safely-managed drinking water services.
Chemistry could bring a solution to this problem identified by the United Nations as Sustainable Development Goal 6 “to change our world” using porous materials, particularly metal-organic frameworks (MOFs). Porous materials like MOFs have a sponge-like chemical structure with microscopic spaces that can selectively trap molecules, from gases—hydrogen, methane, carbon dioxide, water—to more complex substances, such as drugs and enzymes.
While some researchers were focusing on the uses of MOFs in drug delivery and gas purification, Omar Yaghi accidentally discovered their great potential in capturing water from the atmosphere. “When we were studying the trapping of post-combustion gases uptake into MOFs, we noticed that some MOFs exhibited a unique interaction with water molecules,” explains Yaghi. Then, they wondered whether the same material could be used to trap water from the atmosphere in arid climates, and then be released easily for collection.” This technology is unique because, “It can harvest drinkable amounts of pure water from the dry desert air with no energy required other than the natural sunlight,” says Yaghi.
Just one kilogram of MOF could harvest 2.8 liters of water a day at a humidity level as low as 20%. While working on higher capacity, potentially cheaper versions of the water-harvesting materials, Yaghi is “already partnering with companies to test their MOF water harvesters on an industrial scale.” There are other porous materials such as silica-based and inorganic porous solids, and biomimetic porous surfaces that could absorb water from the atmosphere. However, Yaghi argues, most of them are either not as productive as MOFs in taking up water from low humidity air, or require tremendous amount of energy to release the trapped water. MOFs have significant advantages in that regard over other materials and a great potential for making this a sustainable and practical technology to realize off-grid personalized water production, therefore ensuring the progress towards one of the most important UN goals—achieving access to adequate and equitable sanitation and hygiene for all.