Volume 95 Issue 16 | p. 8 | Concentrates
Issue Date: April 17, 2017

Drawing water from dry air

A MOF is at the heart of a sunlight-powered device that pulls water from air with low humidity
Department: Science & Technology
News Channels: Materials SCENE, Organic SCENE
Keywords: metal-organic frameworks, water harvesting
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In this depiction of MOF-801, the yellow, orange, and green spheres represent three different pores. C = black beads, O = red beads, and Zr = blue polyhedra.
Credit: Science
An image of the metal-organic framework MOF-801 used to draw water from air in a new device.
 
In this depiction of MOF-801, the yellow, orange, and green spheres represent three different pores. C = black beads, O = red beads, and Zr = blue polyhedra.
Credit: Science

Finding yourself stranded in the desert without any water could become less of a life-and-death problem, thanks to a new device that can pull potable water from air even in humidity as low as 20% (a condition typical for North Africa). The water harvester, constructed by Evelyn N. Wang’s group at MIT, is powered by only sunlight and has at its heart a metal-organic framework, or MOF, developed by Omar M. Yaghi’s group at the University of California, Berkeley (Science 2017, DOI: 10.1126/science.aam8743). In 2014, Yaghi reported a water-grabbing MOF, known as MOF-801, with the structure [Zr6O4(OH)4(fumarate)6] that could soak up to 25% of its weight in water. He approached Wang about incorporating it in a water-harvesting device. Her group built a prototype with dust-sized crystals of MOF-801 sandwiched between a solar absorber and a condenser plate, which are inside a chamber that’s open to the air. As air flows through the chamber, water attaches to the MOF. Sunlight then heats the MOF, driving the water onto a condenser, where it cools and drips into a collector. Over the course of one day, Wang estimates, a 30-L version of the harvester could collect up to 12 L of water from air, enough to support a single household.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society
Comments
lana (Tue Apr 18 13:28:57 EDT 2017)
I certainly hope that small molecule poisoning of the MOF and particle/fouling layers will not substantially degrade performance over time. I would imagine that it will take significant engineering to ensure consistent water harvesting performance over time with these condensers. I also notice its performance (harvest rate/efficiency) while much better than previous materials, is incredibly dependent on complex interaction of temperature and humidity swings, both magnitude, rate. I really hate having to walk back expectations of public/family/friends from research headlines.

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