CAU-10-H MOF: Harvesting Water From Air

First authors of the publications Lasse Wegner (left) and Kalle Mertin (right) present a prototype water-harvesting cell and a model of the highly porous Metal-Organic Framework (MOF) that the research team has further developed for atmospheric water harvesting and energy-efficient cooling.
Photo Credit: © Christina Anders, Uni Kiel

Scientific Frontline: Extended "At a Glance" Summary: Metal-Organic Framework CAU-10-H

The Core Concept: CAU-10-H is an advanced metal-organic framework (MOF) designed to efficiently extract water molecules from the ambient air to produce drinking water and improve adsorption cooling devices. It operates as a highly porous, sponge-like material capable of rapid and continuous moisture capture and release.

Key Distinction/Mechanism: Unlike traditional desiccants such as silica gel, CAU-10-H effectively captures water at room temperature and low relative humidity (≥18%) and releases it at just 70°C. When synthesized with conductive carbon structures, the composite can be rapidly heated using electricity or sunlight, enabling short, repeatable cycles that yield up to 1.8 liters of water per kilogram of material per day.

Major Frameworks/Components: 

• Metal-Organic Frameworks (MOFs): A class of materials featuring an extremely porous structure with interconnected microscopic cavities for high-capacity adsorption.
• CAU-10-H: The specific MOF optimized for water adsorption and heat transformation, named after its place of discovery, material number, and the chemical symbol for hydrogen.
• Carbon Composites: Conductive carbon structures integrated with the MOF to accelerate the heating and water-release cycles.
• Adsorption Cooling Systems: Technologies utilizing the material's heat transformation properties to deliver up to three times the cooling performance of standard silica gel.

Branch of Science: Chemistry and Materials Science.

Future Application: The continuous generation of drinking water in arid and drought-prone regions, such as the Mediterranean, and the development of sustainable air conditioning systems powered by waste heat from industrial facilities like data centers and bakeries.

Why It Matters: As climate change drives rising temperatures and declining rainfall, CAU-10-H provides a highly efficient, environmentally friendly response to global water scarcity and energy-intensive cooling. Recent pilot-scale production proves the material is economically viable, with projected manufacturing costs of only US$12 to US$14 per kilogram.

Using a model, Kalle Mertin demonstrates the porous structure of CAU-10-H. His arm passing through the model illustrates the material's continuous, tube-like pores, where water molecules are adsorbed and released.
Photo Credit: © Christina Anders, Uni Kiel

Researchers in chemistry and materials science at Kiel University are working with partners to develop new water sources for the Mediterranean region. "Regions like these are facing rising temperatures and declining rainfall. Our goal is to develop an environmentally friendly technology that converts water molecules from the air into drinking water," says Professor Norbert Stock from CAU's Institute of Inorganic Chemistry. "Two new studies, recently published in the Journal of Materials Chemistry A and Industrial & Engineering Chemistry Research, present how large quantities of the material can be produced and how the efficiency of cooling devices can be improved." Furthermore, the researchers demonstrate a new approach that makes water from the air available more efficiently and quickly than previous systems.

A Sponge-Like Material with a High-Tech Structure

Materials belonging to the class of metal-organic frameworks (MOFs) behave much like a sponge: they can adsorb large amounts of water within a short time and release it again just as quickly. This is made possible by their extremely porous structure, which contains countless interconnected microscopic cavities. The fundamental research behind these materials was awarded the 2025 Nobel Prize in Chemistry.

In Kiel, Stock's team is optimizing the synthesis of the MOF CAU-10-H specifically for water adsorption and heat transformation. The material is named after the place of discovery at Kiel University, its material number, and the chemical symbol for hydrogen. CAU-10-H captures water molecules within its porous structure at room temperature and relative humidity values ≥18% and releases them again at around 70°C. By combining the material with conductive carbon structures, the researchers can accelerate this process even further. The resulting composite material can be heated efficiently using electricity or sunlight. As a result, it releases the adsorbed water particularly quickly and operates in short, repeatable cycles. Under dry conditions, the system continuously produces drinking water from the air and achieves a water uptake of up to 0.17 grams of water per gram of material. The cycles take only a few hours, enabling efficient and continuous operation. Under these conditions, one kilogram of the composite material can potentially produce up to 1.8 liters of water from the air per day. "This makes the material particularly attractive for producing drinking water, even in arid regions," says first author Lasse Wegner.

Additionally, CAU-10-H shows considerable potential for cooling applications. In adsorption cooling systems, it delivers up to three times the cooling performance of silica gel, a widely used desiccant based on silicon dioxide. In the future, such systems could make use of waste heat from data centers or bakeries, for example. This significantly reduces the energy consumption of air conditioning systems compared to established technologies, making cooling more sustainable.

From the Lab to Industrial Production

"We discovered CAU-10-H around fifteen years ago, and since then its potential applications have been investigated around the world," says Stock, who has been conducting research on MOFs for more than two decades. Supported by Kiel University's Validation Fund, the team has now successfully transferred production to a pilot scale—the intermediate step between laboratory research and industrial manufacturing. Led by Kalle Mertin, the researchers produced around 30 kilograms of the material, approximately sixty times more than had previously been manufactured in the laboratory. Simultaneously, they further optimized the production process based on a techno-economic analysis to demonstrate that manufacturing costs between US$12 and US$14 per kilogram are achievable. "This brings practical applications of our materials within reach," says Stock. "We have shown that they not only work in the laboratory but can also be produced on an economically viable scale."

Published in journal: 

1. Industrial & Engineering Chemistry Research
2. Journal of Materials Chemistry A

Title: 

1. CAU-10-H: Synthesis Scale-Up at the Pilot Scale, Techno-Economic Analysis, and Application in a Full-Scale Cooling System
2. Electrically conductive MOF@carbon foam composites for atmospheric water harvesting through internal Joule heating and light irradiation

Authors: 

1. Kalle S. Mertin, Abeer Mohtar, Marta Bordonhos, Moisés L. Pinto, Thomas May, Ralph Herrmann, and Norbert Stock
2. Lasse Wegner; Philipp Schadte, Ravi Sharma, Carde Reimerdes, Rainer Adelung, Joeri F. M. Denayer, Leonard Siebert, and Norbert Stock

Source/Credit: Kiel University

Edited by: Scientific Frontline

Reference Number: chm071326_01

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