Off-Grid Devices Draw Drinking Water from Dry Air

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Access to water is already a problem for the third of the world’s population who live in arid regions of the world, and it will only get worse as droughts become more severe with climate change. But what if there was a way to extract water from the air? Until now, that’s only been possible in areas of high humidity, and using large amounts of power. Now, new solar solar systems are bringing down the cost of power, and new materials—metal organic frameworks (or MOFs)—are making it possible to absorb water from the air even when the humidity is as low as 20%.

Beyond their versatility, MOFs’ great promise lies with their phenomenally large pores: the surface area inside is almost 10 times that of porous zeolites. For context, one gram of an MOF crystal the size of a sugar cube has an internal surface area approximately equal to the area of a football field.

In April Yaghi’s group, along with that of M.I.T. mechanical engineer Evelyn Wang, reported on a prototype device incorporating MOF-801 (zirconium fumarate), which has a high affinity for water. It pulls moisture from the air into its large pores and readily feeds the water into a collector in response to low-grade heat from natural sunlight. The device can harvest 2.8 liters of water daily per every kilogram of MOF even at relative humidity levels as low as 20 percent, similar to the humidity of deserts, and it requires no additional input of energy.