The crystal structure of the super-adsorbent Cr-soc-MOF-1, which can adsorb twice its weight in water within its extensive network of micropores. The MOF framework is represented in green, red and grey, while water molecules are represented as blue spheres. Image: (c) 2018 Mohamed Eddaoudi.
The crystal structure of the super-adsorbent Cr-soc-MOF-1, which can adsorb twice its weight in water within its extensive network of micropores. The MOF framework is represented in green, red and grey, while water molecules are represented as blue spheres. Image: (c) 2018 Mohamed Eddaoudi.

Humidity control is a vital aspect of air conditioning, but high energy requirements make conventional methods expensive and environmentally damaging. Researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have now developed a metal-organic framework (MOF) that, within its range of applications, could control humidity in an eco-friendly and cost-effective way.

MOFs encompass metal centers or clusters held in a porous framework by organic linker groups. The key to designing a MOF with specific properties is being able to control the size and chemical structure of the pores by varying the metal and organic parts within each framework.

Dalal Alezi works in Mohamed Eddaoudi's research group at KAUST, where a wide range of MOFs are being developed for gas separation, purification and chemical catalysis. This current work, reported in a paper in Chem, forms part of her doctoral research.

"Our super-adsorbent material has unique properties," explains Alezi. Two breakthrough achievements with the new water-adsorbing MOF, termed Cr-soc-MOF-1, are its unusual stability in water and its high-capacity internal pores that allow the MOF to adsorb twice its weight in water. Another vital feature is the easy reversibility of the water uptake: the water adsorbed when humidity levels are high can readily be released when the humidity falls. This yields an ideal material for controlling humidity in restricted spaces.

"Regulating escalating humidity levels, especially indoors and in confined environments, such as aircraft cabins and air-conditioned buildings, is a critical challenge," says Youssef Belmabkhout, a senior research scientist in Eddaoudi's group. "The conventional systems consume large amounts of energy, require intricate design and excessive cost."

This new material is just one product of Eddaoudi's long-term commitment to exploring the capabilities of MOFs. "To the best of our knowledge our new water-adsorbing MOF outperforms all existing MOFs in terms of capacity, reversibility and cyclic performance," says Eddaoudi. The easy reversibility will be crucial for commercial applications; the team have already maintained the exceptional water uptake and release through more than 100 adsorption-desorption cycles.

Eddaoudi also emphasizes that water-adsorbing MOFs are ready to provide effective solutions to other challenges, such as tackling water scarcity and environmental sustainability, in energy-efficient ways. Possibilities include using the MOFs to harvest drinkable water from air and for water desalination and purification.

The researchers are now working to scale up their water-adsorbing materials in order to demonstrate commercial potential and move into real-world applications.

This story is adapted from material from KAUST, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.