Atmospheric water is a resource equivalent to~10% of all fresh water in lakes on Earth. However, an efficient process for capturing and delivering water from air, especially at low humidity levels (down to 20%), has not been developed. We report the design and demonstration of a device based on a porous metal-organic framework {MOF-801, [Zr 6 O 4 (OH) 4 (fumarate) 6 ]} that captures water from the atmosphere at ambient conditions by using low-grade heat from natural sunlight at a flux of less

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... an 1 sun (1 kilowatt per square meter). This device is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20% and requires no additional input of energy.