Potable Water Out of Desert Air

by | 11. Jan 2024 - 10:40 | Technologies

Research team develops unique microporous material made of hafnium and zirconium for water adsorption.

The supply of drinking water is already critical in many arid regions of the world – a situation that is being exacerbated by advancing climate change. One possible solution currently being researched is the extraction of water from the ambient air, as even in the driest regions of the world, there is a certain amount of humidity.

A material based on the metals zirconium and hafnium, developed by a team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Technische Universität Dresden (TUD), could prove helpful. These are so-called MOFs (from “metal-organic frameworks”), a class of materials known for around 25 years: artificial networks of metal ions and organic molecules as connecting elements. MOFs have an open, highly porous structure, similar to the pores of a kitchen sponge, and an enormously large inner surface area. They can be used for various potential applications such as gas storage, separation of substances, catalysis, sensor technology, or as a medicine depot. According to the HZDR, water extraction is a particularly promising process.

In their research work, the team synthesized two MOFs based on zirconium and hafnium, held by the same organic framework. In nature, the two elements always occur together. Subsequent investigations using various techniques confirmed that the materials have a high adsorption capacity, according to a study published in the journal ACS Applied Materials & Interfaces. Due to the remarkable similarity of zirconium and hafnium, the resulting metal-organic frameworks are characterized by the exact pore sizes and high chemical stability, explains Stefan Kaskel, holder of the Chair of Inorganic Chemistry I at TU Dresden.

Organometallic framework compounds can reversibly absorb water from the air in the pores they form.

Photo: B. Schröder/ HZDR

Basis for Future Materials for Water Extraction Out of Air

The study also provides insights into the general mechanism of water adsorption by MOFs, which needs to be better understood. On this basis, better materials for water extraction from the air could be developed in the future, for example, in adsorption-driven heat pumps: MOFs that capture water molecules from the atmosphere and rerelease them by adding heat or reducing pressure.

However, there is still much to do before the technology can be used commercially, including finding cost-effective solutions for producing large quantities of MOFs. As this requires new environmentally friendly manufacturing processes, the team at TU Dresden is already using the corresponding principles of “green chemistry.”

More innovation: “wonder materials” MOFs – the artificial networks could also contribute to many other challenges of our time, such as neutralizing exhaust gases or disarming chemical weapons.

Photo: iStock/hadynah

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