Imagine that Santa Claus gives you a big box of new Lego bricks that allow you to build things that previously just collapsed. This year's chemistry laureates have discovered such a box.
Susumu Kitagawa, Richard Robson and Omar Yaghi are awarded the 2025 Nobel Prize in Chemistry for developing a new form of molecular architecture. Metal ions are linked to carbon-based molecules to form regular crystals with cavities inside. These are called metal-organic frameworks (MOFs), and various substances can be captured and stored in the cavities.
“It's a conceptual Nobel Prize. The laureates' approach to chemistry is a bit like that of a builder or architect who wants to create a structure with a particular appearance. The laureates have found a way to define the direction based on the bond between the organic molecule and the metal ion,” says Karl Börjesson, Professor of Physical Chemistry at the University of Gothenburg.
Based on bond angles
There are already stable and hollow materials, zeolites, that can be built cheaply from silicon dioxide. But zeolites are usually hard, while MOFs contain flexible molecular building blocks that can create mobility in the material. It is also possible to build different functions into them.
The construction is based on bond angles. Organic compounds with free electron pairs at the ends can connect with metal ions and create a crystal-like structure. Depending on which metal ion the chemist chooses to build with, you get different angles on the created crystal, and the size of the organic compound affects the size of the cavities. In this way, chemists can tailor MOFs so that cavities are formed in the crystals where different substances can be captured.
In some MOFs, the cavities are really large and therefore have the ability to capture large amounts of a gas, for example. Omar Yaghi built a metal-organic framework where a few grams of the structure had cavities the size of a football field.
Over the past few decades, researchers have built a wide variety of functional MOFs. In most cases, however, the materials have only been used on a small scale. In pilot studies, researchers are demonstrating how metal-organic frameworks can be used to extract water from desert air at night or capture carbon dioxide from the atmosphere.
Hundreds of start-up companies are now working to commercialise the discovery of MOFs, and many future applications are just around the corner.
“There are applications that have nothing to do with gases; it is possible to build a membrane that can filter substances on a nanometre scale. This could be used to filter hydrocarbons that currently have to be distilled apart. A fellow researcher is investigating whether a MOF could be used as a filter that connects electronics and the body's signalling substances,” says Karl Börjesson.
