Nobel Prize in Chemistry, 2025

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Chemistry 2025 to Susumu Kitagawa, Richard Robson and Omar M. Yaghi “for the development of metal–organic frameworks.”

The laureates developed a new type of molecular architecture. The constructions they created called metal–organic frameworks, contain large cavities in which molecules can flow in and out. Researchers have used them to harvest water from desert air, extract pollutants from water, capture carbon dioxide and store hydrogen.

What are organic compounds?
An organic compound is a chemical substance built around carbon atoms covalently bonded to hydrogen. They often include oxygen, nitrogen, and other elements. They are named so because they form the basis of all life. They are also used to make materials like plastics, fuels, and medicines. Their vast diversity comes from carbon's ability to form strong, complex chains and rings, creating essential molecules like proteins, carbohydrates, fats, and DNA.

UNTITLED BOX
The Nobel Prize laureates in chemistry 2025 have created molecular constructions which have large spaces through which gases and other chemicals can flow. These constructions are called metal–organic frameworks (MOF). As you may have learned in your chemisty classes, metals are not usually combined with organic compounds. A rare example is a Vitamin B12 co-enzyme containing a rare, naturally occurring cobalt-carbon bond. They have practically unlimited uses: they can be used to harvest water from desert air, capture carbon dioxide, store toxic gases or catalyse chemical reactions. Through the development of these frameworks, they have provided chemists with new opportunities for solving some of the challenges we face in today's world.
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The Robson story
It was 1974, fifty years ago. Richard Robson, who was teaching at the University of Melbourne, Australia, had been tasked with making models of atoms using wooden balls and sticks, so that students could create molecular structures. For this to work, he needed the university’s workshop to drill holes in them, so that the wooden rods which represented the chemical bonds, could be attached to the atoms.
He started with a very simple model, inspired by the structure of a diamond, in which each carbon atom bonds to four others, forming a tiny pyramid (see figure). Robson’s aim was to build a similar structure, but his would be based on positively charged copper ions, Cu+. Like carbon, they prefer to have four other atoms around them.
He combined the copper ions with a molecule that has four arms. Its name is complicated: 4′,4″,4”’,4””-tetracyanotetraphenylmethane but not important for this story. What is relevant is that the molecule at the end of each arm had a chemical group called nitrile, that was attracted to the positively charged copper ions (see figure).
As he had predicted, the attractive forces between the ions and molecules caused them to organise themselves into a large molecular construction. Just like carbon atoms in a diamond, they formed a regular crystalline structure. However, unlike diamond – which is a compact material – this crystal contained a vast number of large cavities.
Fifteen years later, in 1989, Robson presented his innovative chemical creation in the Journal of the American Chemical Society. In this article, he suggests that this could offer a new way to construct materials. These could have never previously seen properties, potentially beneficial ones. He actually foretold the future, which was made possible by the other two Nobel winners.

Susumu Kitagawa, twenty years later ...
When Kitagawa began to investigate the potential for creating porous molecular structures, he did not believe they had to have a specific purpose. When he presented his first molecular construction in 1992, it was indeed not particularly useful: a two-dimensional material with cavities in which acetone molecules could hide. However, it had resulted from a new way of thinking about the art of building with molecules. Like Robson, he used copper ions as cornerstones that were linked together by larger molecules.

UNTITLED BOX
As a young student, Susumu Kitagawa read a book by the Nobel Prize laureate Hideki Yukawa where he refers to an ancient Chinese philosopher, Zhuangzi, who says: we must question what we believe to be useful. Even if something does not bring immediate benefit, it may still turn out to be valuable. This greatly influenced his work.
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In 1997 Kitagawa had his first major breakthrough. Using cobalt, nickel or zinc ions and a molecule called 4,4′-bipyridine, his research group created three-dimensional metal–organic frameworks that were intersected by open channels (see figure). When they dried out one of these materials – emptying it of water – it was stable and the spaces could even be filled with gases. The material could absorb and release methane, nitrogen and oxygen, without changing shape.

What was the reaction of the community?
Zeolites are stable and porous materials, which can be built from silicon dioxide. These were already researched and known to absorb gases. So why would anyone develop a similar material that did not work as well?
Kitagawa had a simple response: these MOFs can be created from many types of molecules, so there can be many many applications. Also – and this is important – he realised that MOFs can form soft materials. Unlike zeolites, which are usually hard materials, MOFs contain flexible molecular building blocks (see figure) that can create a pliant material which easily bends.

UNTITLED BOX
Studying chemistry was not an obvious choice for Omar Yaghi. He and his many siblings were raised in a single room in Amman, Jordan, with no electricity or running water. School was a refuge from his otherwise challenging life.
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Omar Yaghi's Rational Designs
Normally, chemists make substances combine by heating them, applying pressure, using a catalyst, etc. The desired molecule forms, but it is also often accompanied by a range of contaminating side products.
Omar Yaghi, at Arizona State University, wanted to find more controlled ways in which to create materials. His aim was to use rational design to connect different chemical constituents, like pieces of Lego, to make large crystals. This turned out to be challenging, but they finally succeeded when the research group started combining metal ions with organic molecules.
In 1995, Yaghi published the structure of two different two-dimensional materials; these were like nets and were held together by copper or cobalt. The latter could host guest molecules in its spaces and, when these were fully occupied, it was so stable that it could be heated to 350°C without collapsing. Yaghi described this material in an article in Nature where he first coined the name “metal–organic framework.” This term is now used to describe all such ordered molecular structures that potentially contain cavities, and which are built from metals and organic (carbon-based) molecules.

Breathing like lungs
Yaghi established the next milestone in the development of metal–organic frameworks in 1999, when he presented a specific molecule called MOF-5 to the world. This material has become a classic in the field. It is an exceptionally spacious and stable molecular construction. Even when empty, it can be heated to 300°C without collapsing.
However, what caused many researchers to raise their eyebrows was the enormous area hiding inside the material’s cubic spaces. A couple of grams of MOF-5 holds an area as big as a football pitch, which means it can absorb much more gas than a zeolite could (see figure).
Speaking of the differences between zeolites and MOFs, it took just a few years for researchers to succeed in developing soft MOFs. One of those who was able to present a flexible material was Susumu Kitagawa himself. When his material was filled with water or methane, it changed shape, and when it was emptied, it returned to its original form. The material behaved somewhat like a lung that can breathe gas in and out, changeable but stable.
One thing he did was to produce 16 variants of MOF-5, with cavities that were both larger and smaller than those in the original material (see figure). One variant could store huge volumes of methane gas, which Yaghi suggested could be used in RNG-fuelled vehicles.
Subsequently, metal–organic frameworks have taken the world by storm. Researchers have developed a molecular kit with a wide range of different pieces that can be used to create new MOFs. These have different shapes and characters, providing incredible potential for the rational – or AI-based – design of MOFs for different purposes. The figure provides examples of how MOFs can be utilised.
For instance, Yaghi’s research group has harvested water from the desert air of Arizona. During the night, their MOF material captured water vapour from the air. When dawn came and the sun heated the material, they were able to collect the water.
Some researchers believe that metal–organic frameworks have such huge potential that they will be the material of the twenty-first century. Time will tell, but through the development of metal–organic frameworks, Susumu Kitagawa, Richard Robson and Omar Yaghi have provided chemists with new opportunities for solving some of the challenges we face. They have thus – as Alfred Nobel’s will states – brought the greatest benefit to humankind.
Source: nobelprize.org