Session: Chemistry of Materials:

Developing alternative strategies to produce potable water is of fundamental importance to address the water shortage crisis, which is projected to intensify in the next years due to global warming and population growth. Sorbent-assisted atmospheric water extraction (AWE) could be a viable strategy to tap the ubiquitous atmospheric moisture and allow for off-grid freshwater access at any time and anywhere—even in arid regions, where water is most needed. In this context, synthesis and implementation of next-generation sorbents, such as metal-organic frameworks (MOFs), is essential to unleash the full potential of this technology.
Hitherto, sorbents developed for AWE have been exclusively designed to perform one water harvesting cycle per day, but the productivities attained with this approach are inherently limited by the sorbent’s capacity. Our work shows that the microporous aluminum-based MOF-303 (Fig. 1a) can perform an adsorption-desorption cycle within minutes under a mild temperature swing, which opens the way for high-productivity water harvesting through rapid, continuous cycling. Additionally, the favorable dynamic water sorption properties of MOF-303 (Fig. 1b) allow it to outperform other commercial sorbents displaying excellent steady-state characteristics under similar experimental conditions. Finally, these findings are implemented in a new water harvester (Fig. 1c) capable of generating ~1 L per kg_mof and day in the Mojave Desert (in conditions as extreme as 10% RH, 27 °C), representing an improvement by 1 order of magnitude over previously reported devices. This study demonstrates that creating sorbents capable of rapid water sorption dynamics, rather than merely focusing on high water capacities, is crucial to reach water production on a scale matching human consumption.

<b>Fig. </b><b>1</b><b>:</b> <b>Water harvesting with MOF-303. </b>a) MOF-303 and its water sorption isotherm at 25 °C. b) Sorption kinetics of a thin layer at different relative humidities (RH). c) Schematic representation of the cyclic water harvester and its functioning principle.

Fig. 1: Water harvesting with MOF-303. a) MOF-303 and its water sorption isotherm at 25 °C. b) Sorption kinetics of a thin layer at different relative humidities (RH). c) Schematic representation of the cyclic water harvester and its functioning principle.

Omar Yaghi

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