Nobel Prize winners created large spaces to capture molecules

A marriage between the two classical branches of chemistry – the once strictly separated organic and inorganic chemistry – is being celebrated with a Nobel Prize after more than forty years. On Wednesday, Susumu Kitagawa, Richard Robson and Omar M. Yaghi won the Nobel Prize in Chemistry for developing “a new kind of molecular architecture”: metal-organic frameworks.

This metal-organic frameworks (MOFs) combine the enormous versatility of organic chemistry – old-fashioned cut-and-paste chemistry that focuses on carbon – with the special properties of inorganic chemistry – the chemistry of metals. The Nobel Committee sees MOFs as having “enormous potential to create tailor-made materials with new functions,” Nobel Committee chairman Heiner Linke said at the time of the announcement.

The metal-organic frameworks, as the name suggests, consist of metal atoms linked together by organic molecules. Put the right building blocks together in a solution and three-dimensional, angular molecular structures will automatically arise. This contains large spaces into which other molecules can flow, possibly remain trapped and disappear again in a controlled manner.

This allows a MOF to act like a molecular sponge. The large surface area hidden in that sponge is also special: the MOF type 5, which Yaghi presented in 1999, has the size of a sugar cube and an internal surface area of ​​a football field. “When we published the first results in the mid-1990s, our colleagues thought there was a printing error in the article,” Yaghi said against this year de Volkskrant. It contains a structure of billions of holes, a kind of “parking lot for water molecules”.

In this way, the frameworks can still capture substances that are normally elusive. In 2023, Yaghi students managed to pull water from the desert air with ‘MOF-303’. And one of the driest in the world: Death Valley in the United States. She published in the scientific journal NatureWater.

The same is possible, for example, with PFAS, the group of thousands of different substances that constitute a major pollutant in the environment. They’re everywhere.

Yaghi’s name has been around in recent years

Bert Weckhuysen, professor of inorganic chemistry at Utrecht University, happens to be on the train to a conference in Brussels where Yaghi will speak on Thursday morning. “I expected this prize,” he says, “Yaghi’s name has been around in recent years. The question was rather which people would receive the prize together. I think the Nobel Committee made the right choice, because older work is also involved.”

That older work is that of Richard Robson, who came up with the concept of the MOF in 1989. He was inspired by the crystal structure of diamonds, which consist of a regular lattice of carbon atoms in a pyramid shape. He thought that something similar should be possible based on metal ions and organic molecules. But while the carbon atoms in diamond are close together, the grid of the MOFs is extremely spacious. The cavities in the grid are so large that other molecules can easily fit between them – to engage in a chemical reaction, for example.

Robson’s frameworks were still unstable, which is why many chemists considered them “useless” for a long time. In the 1990s, Susumu Kitagawa succeeded in creating stable MOFs, and even in making the structures flexible, giving them their sponge-like effect. Gases can flow in and out of the structures. .

Yaghi subsequently developed the concept of a niche into a mature and fully-fledged field within chemistry. Depending on the design of the organics in the grid, the possibilities of MOFs are endless. He created several variants of even more stable MOFs, making the promise of the field clear to everyone. More than 90,000 different MOFs have now been made.

‘Prolonged buffalo’

“I think Yaghi is very happy,” says Weckhuysen, who knows him, “because he had a lot of resistance in the beginning. From the first line of thought, it has been a long struggle, and now there are a kind of grilles that breathe. You can apply it according to application, that is fantastic.”

Are MOFs still primarily a versatile and interesting chemical toy with promising applications, or have they become indispensable? A bit of both: MOFs are still very expensive, making large-scale use difficult. Nevertheless, scaling up has begun and there are plenty of applications, such as CO₂capture or a PFAS cleanup agent. According to the site Global Market Insights the market was already worth $9.8 billion in 2024, and could be three times as large in ten years.

“MOFs are the most beautiful connections ever made,” wrote Yaghi an opinion contribution on the site in 2019 Chemistry World. “Their structures are complex and I find the diversity of structural patterns and connectivity fascinating. I like looking at molecular structures and the periodic table, and how that translates into compounds, reactions, materials and new chemistry.”

With the collaboration of Niki Korteweg and Gemma Venhuizen.

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