MOFs are porous crystalline materials made by connecting metal-containing nodes with organic molecules called linkers.
The resulting structures can have exceptionally large internal surface areas relative to their mass.
To understand why this matters, imagine a small sponge.
A sponge appears compact from the outside, but its internal spaces allow it to absorb and hold water. The amount it can retain depends on its structure and the characteristics of the liquid.
Now imagine a material engineered with pores measured in nanometres, where the internal architecture is designed at the molecular level.
Instead of simply soaking up liquid water, such a material can interact with water molecules in humid air.
Scientists can adjust its chemistry to influence how readily those molecules enter the pores, how strongly they bind to the internal surfaces, and how easily they can be released later.
The result is not an ordinary sponge. It is a highly engineered material whose behaviour can be tailored for a specific purpose.
This is one reason Yaghi's work has attracted such considerable interest.
His research helped establish reticular chemistry as a powerful way of designing porous materials rather than treating their structures as something that must simply be accepted after synthesis.
In 2025, Yaghi was awarded the Nobel Prize in Chemistry alongside Susumu Kitagawa and Richard Robson for the development of metal-organic frameworks.
The recognition reflected decades of scientific work that helped open a new field of materials chemistry.
The significance of this research extends well beyond any single water-harvesting device.
A material designed to capture water may also inspire related approaches to gas storage, carbon capture, and other challenges where the selective interaction of molecules is important.
The same underlying principle remains central: if scientists can design the internal structure of a material with sufficient precision, they can potentially give it useful capabilities that conventional materials do not possess.
And when the target molecule is water, those capabilities may help address one of the world's most fundamental needs.
How Can Anyone Extract Water From Thin Air?
7
At first, the idea of obtaining water from air seems almost impossible.
When people picture a desert, they often imagine endless sand, scorching sunlight, and an environment where water has disappeared entirely.
Yet the atmosphere can contain water vapour even in extremely dry regions.
Humidity measures the amount of water vapour in the air relative to the amount it could hold at a given temperature. Warm air can generally contain more water vapour than cold air, although the actual amount present depends on local weather conditions.
Even when relative humidity is low, the air is not necessarily completely dry.
The problem is that water vapour is invisible and dispersed. It cannot simply be poured into a container, and conventional collection methods often require the air to be cooled sufficiently for the vapour to condense.
That can consume substantial energy, especially when the atmosphere is hot and dry.
Atmospheric water harvesting takes a different approach.
Instead of relying exclusively on cooling air until water condenses, some systems use materials specifically designed to capture water molecules from the surrounding atmosphere.
These materials act as water collectors at a microscopic level.
Their internal pores provide places where water molecules can be attracted and held. Once the material has collected sufficient moisture, heat can be applied to release the captured water vapour.
The vapour can then be directed to a cooler surface, where it condenses into liquid droplets.
Those droplets can be collected in a reservoir.
The process can be summarized in four main stages:
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Capture: Air passes over or through a porous material that attracts water molecules.
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Accumulation: Moisture gathers within the material's internal pores.
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Release: Heat, potentially supplied by sunlight, helps drive the captured water back into the vapour phase.
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Collection: The released vapour condenses and is collected as liquid water.
The material can then be used again, allowing the process to repeat.
The key is that the material does not create water from nothing. It captures water that already exists in the atmosphere and concentrates it into a form that can be collected.
This distinction is scientifically important, but it does not make the achievement any less remarkable.
Turning a widely dispersed substance into a useful resource is a central challenge in many areas of engineering.
Water-harvesting systems must perform this task efficiently, reliably, and at a cost that makes sense for the communities expected to use them.
A material that captures water in a laboratory is an important scientific accomplishment. A complete system that can operate for years in a remote village, withstand dust and heat, and deliver safe drinking water at an affordable price is a much larger engineering challenge.
The most promising research seeks to bridge that gap.
The Tiny Pores That Make a Big Difference
The most fascinating aspect of this technology is that much of its work happens on a scale far too small for the human eye to see.
The porous materials used in atmospheric water harvesting can contain an immense number of microscopic spaces. Their properties are determined not simply by how many pores they possess, but by the chemistry and geometry of those pores.
Water molecules interact with surfaces through forces that are weak compared with the bonds holding molecules together, yet powerful enough to influence how molecules gather within a material.
In a carefully designed framework, the pore walls can contain chemical groups that attract water.
When humid air comes into contact with the material, water molecules can enter the pores and begin accumulating.
As the amount of water increases, the behaviour of the material depends on factors including temperature, pressure, pore dimensions, and the chemical affinity between the framework and water.
A well-designed material needs to balance several competing requirements.
First, it must attract water even when the atmosphere contains relatively little moisture.
Second, it should be capable of holding a useful quantity of water without requiring an excessive amount of material.
Third, the water must be released at a temperature that is practical to achieve, ideally using sunlight or another readily available heat source.
Finally, the material must remain stable through repeated cycles of capturing and releasing moisture.
These requirements are more difficult to satisfy simultaneously than they might initially appear.
A material that binds water extremely strongly may capture it effectively but require too much energy to release it. Another material might release water easily but fail to collect enough moisture under dry conditions.
The goal is to find the right balance.
Scientists can modify the chemical building blocks, alter the arrangement of pores, and investigate how different structures behave at varying humidity levels.
Computer modelling and laboratory experiments help researchers understand the interactions involved.
A material can then be tested under conditions that approximate the environment in which it might eventually be used.
For example, a device intended for a hot desert must be evaluated differently from one designed for a humid coastal community.
The desert system may need to capture water when humidity is low and temperatures are high. The coastal system may encounter abundant atmospheric moisture but also corrosive salt, changing weather, or persistent humidity that affects the device's operating cycle.
In each case, the microscopic structure of the material helps determine the system's practical performance.
This is where reticular chemistry offers a particularly valuable advantage.
Instead of merely searching through existing substances and hoping to find one that performs well, researchers can design frameworks with specific molecular properties in mind.
The result is a pathway toward materials that can be tailored to different environments and applications.
What appears to be a small collection of powder or crystals can therefore become the foundation for a sophisticated water-collection system.
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Capturing moisture is only part of the process. The system must also release that moisture so it can be collected.