These porous complexes of metal ions and organic molecular chains form cage-like cavities that can trap other chemicals. This allows them, for example, to capture CO2 or water from the air, store gases or serve as a selective barrier. The award winners Susumu Kitagawa, Richard Robson and Omar Yaghi discovered and further developed this new class of materials.
Whether as a CO2 capturer in direct air capture, as an aid in water extraction or purification or as an electrode material in batteries: the highly porous cage molecules of the metal-organic framework compounds are as versatile as they are practical. Depending on which metal ions and organic “support struts” these materials contain, they selectively store and bind a wide variety of chemicals. The 2025 Nobel Prize in Chemistry will go to three chemists to whom we owe these versatile framework compounds.
Wooden balls, sticks and an idea
The story of this discovery begins in the 1970s, when Richard Robson, then a chemistry professor at the University of Melbourne, was preparing a chemistry lecture for his students. They should assemble molecular structures using pre-drilled wooden balls and rods. This showed that the holes for the connecting rods had to be located in different places on the spheres depending on the type of atom and molecule. Robson recognized that the intrinsic properties of atoms shape the structure of the resulting molecules. This led the chemist to ask the question: Could one create novel, tailor-made molecular structures simply by choosing the right “balls” and holes?
For his first experiments, Robson chose copper ions as “spheres,” which he combined with organic nitriles—polar compounds with a triple bond of carbon and nitrogen at one end. Due to the partial charges at the end of the nitriles, they accumulated on their own in such a way that they formed struts between the copper ions. The result was a lattice structure similar to that of the diamond, but with large cavities between the struts. Robson recognized the potential of these porous scaffolds: in his experiments, he used the scaffold molecules to trap various other chemicals in the cavities. It turned out that these metal-organic frameworks could also function as ion exchangers: Because they bind some foreign ions better than others, they can be used as chemical filters or storage. In 1989 Robson published his findings on this new class of materials. However, its metal-organic frameworks were still very unstable and not very robust.
Channels and flexible scaffolding
This is where the achievements of the other two Nobel Prize winners come into play. Independently of each other, they developed new, stable variants of the three-dimensional metal-organic framework compounds based on initially two-dimensional constructs and demonstrated completely new properties and advantages of these molecular cages. In 1997, Susumu Kitagawa from Kyoto University discovered that the metal-organic frameworks could be designed so that they contain permeable channels and can bind or let gases through. The chemist was also the first to develop cage molecules that were not rigid, but rather bendable and flexible. In 1998, Kitagawa described how stable scaffolding molecules could be created from very different basic building blocks – which increased the enormous application potential of the materials.
The next milestone in the development of metal-organic framework compounds was achieved by Omar Yaghi from the University of California at Berkeley in 1999: The chemist developed a framework molecule, MOF-5, which is still groundbreaking today. This combination of zinc oxide ions and chains of the plastic terephthalate is stable even at temperatures of up to 300 degrees and forms particularly large cavities. In the early 2000s, Yaghi and his team developed scaffolding compounds that are suitable for storing methane gas or that can capture water vapor from the air – for example to produce drinking water in desert regions.
“Enormous potential”
There are now tens of thousands of different metal-organic framework compounds and their potential is not even close to being exhausted. They can help clean water and air of harmful chemicals like PFAS or pesticides, capture greenhouse gases from the atmosphere, or convert gaseous resources like hydrogen into transportable form. “Organic metal framework compounds have enormous potential and open up previously unimagined possibilities for tailor-made materials with new functions,” says Heiner Linke, Chairman of the Nobel Committee for Chemistry.
Source: The Royal Swedish Academy of Sciences