Nobel Prize-winning metal-organic frameworks are the jungle gyms of chemistry

This year the Nobel Prize in Chemistry went to three scientists — Susumu Kitagawa, Richard Robson and Omar M. Yaghi — for the development of metal-organic frameworks (MOFs), which may one day be used to harvest drinkable water from desert air, to store and degrade toxic gases or even serve as drug delivery systems.

University of California San Diego Distinguished Professor of Chemistry Seth Cohen has made a career out of studying and developing MOFs. He worked at the Defense Advanced Research Projects Agency (DARPA), where he created and managed a program called Atmospheric Water Extraction, which funded Yaghi’s work on developing MOFs to extract water from air. Currently, Cohen’s lab at UC San Diego is working to develop modified MOFs with new characteristics and capabilities. Here he explains what MOFs are, how they work and the great promise they hold.

What are metal-organic frameworks and what can they do?

A MOF is a material that, at the molecular level, looks like a jungle gym.

Cohen is also a Chancellor's Distinguished Professor in Chemistry and Biochemistry.

It's a huge lattice that is mostly empty space inside. If you think about a jungle gym, the reason kids play inside it is because even though it's big, it's really mostly empty spaces. That's exactly what a MOF looks like, where the rods of the jungle gym are the organic component, and the struts, where they connect, are the inorganic metal component.

The consequence of these lattice-like structures is that you can make materials that have huge amounts of internal voids. So much so that they can basically act like a molecular sponge, absorbing all kinds of things at huge capacities, including water, methane, carbon dioxide and even pharmaceuticals.

So along those lines, the questions the field has explored are: Could MOFs capture water from the air to provide drinking water to someone? Could you capture and store hydrogen for hydrogen-powered cars? Could you capture carbon dioxide from power plants to mitigate pollution? Could you use MOFs in timed drug delivery by storing drug molecules inside the lattices and then having them release slowly?

To give you a real-world example, let’s go back to the hydrogen- or methane-powered vehicle. The tank is empty and you put gas into it until it’s full. But here's the crazy thing about MOFs: let’s say you filled the tank with a bunch of MOFs, which look like table salt. Now when you look in that tank, it's filled with all this crystalline, solid stuff. Your initial reaction would be, well, you're going to get a lot less methane in there, because you've filled up the space with all of this solid material. But, actually, each of those MOF crystals has all that surface area inside. So what happens is that same tank, even though it looks like it's filled with this solid material, will hold many times more methane than the empty tank will.

MOFs are basically the lowest density, highest porosity solid material ever created and it is these properties (among others) that has made them the source of such excitement and interest in the chemistry community, culminating in the 2025 Nobel Prize in Chemistry.