Nobel Prize in chemistry awarded to architects of metal-organic frameworks

By ALEXA ROBLES-GIL and ALI WATKINS

Susumu Kitagawa, Richard Robson, and Omar M. Yaghi were awarded the Nobel Prize in chemistry Wednesday for the development of molecular building blocks with spaces large enough that gases and other chemicals can flow through them.

The cavities on the inside are “almost like rooms in a hotel, so that guest molecules can enter and also exit again from the same material,” Heiner Linke, chair of the Nobel Committee for Chemistry, said during the announcement of the award. The laureates’ discoveries, he added, paved the way for the creation of materials that can separate toxic chemicals from wastewater or harvest water molecules in a desert.

The laureates’ work started with experiments by Robson in the 1980s and gradually developed over a period of about 15 years.

“It takes time for science to be recognized, and it takes multiple workers in the field with different approaches,” said Dorothy Phillips, president of the American Chemical Society.

The three laureates will share a prize of 11 million Swedish kronor (around $1.17 million).

Why did the Nobel Committee say they received the prize?

The scientists are responsible for developing a new kind of molecular structure that combined metals and organic molecules. The metals act as nodes and are linked up by organic molecules containing carbon. Large, empty spaces form inside these structures through which gases and other materials can flow.

Robson first experimented with metal-organic frameworks in 1989, when he combined copper ions with four-armed molecules, the committee said. The result was a sort of crystal with large cavities, indicating that other molecules might be able to move in and out of the framework easily.

But the structure was unstable and collapsed quickly. That initial experiment was built on by Kitagawa and Yaghi, whose work from 1992 to 2003 helped stabilize the framework Robson had created, the committee said.

In chemistry, molecules arrange themselves in unpredictable structures. The scientists were able to combine metals and organic molecules as “building blocks,” so that even if the size of the clusters change, you would still get the same structure but with larger cavities inside, said Kim Jelfs, a computational chemist at Imperial College London.

That level of control within chemistry has “always been a challenge,” she said. “So that’s part of the excitement.”

The scientists’ experiments laid the foundation for the development of thousands of metal-organic structures with many real-world applications, like trapping gas emitted by fruit so it ripens more slowly.

It has “sparked a whole field,” Jelfs said. “There’s an enormous number of people that work in this area now.”

One commercial application for metal-organic frameworks is a technology that contains toxic gas during the production of semiconductors, according to a summary posted by the Nobel committee. The porous structure acts like a sponge that sucks in more gas than traditional materials are capable of holding.

The scientific field around metal-organic frameworks is focused on higher complexity applications. “We’re just scratching the surface,” said Amanda Morris, a chemist at Virginia Tech.

Yaghi is currently working on those applications. He’s the founder of Atoco, a startup that is working on technologies that can harvest water and capture carbon. These technologies are made from materials that use metal-organic frameworks.

In capturing water, for instance, the frameworks act as a sponge with a higher surface of pores to absorb more volume per mass. In previous experiments, a metal-organic framework Yaghi’s group worked with captured water vapor at night then used the heat of the sun to convert it into water the next day.

Who are the winners?

Robson is a professor at the University of Melbourne in Australia, where he has taught since 1966. In a phone interview posted by the Nobel committee, Robson, 88, said there were “upsides and downsides” to the news of the prize.

“I’m quite old now, and handling all the nonsense that’s going to happen is going to be hard work,” he said.

Robson recalled he “always felt sort of second rate for not being a mathematician” as a younger scientist, and drifted into the field of chemistry because he “couldn’t think of anything better to do.”

Kitagwa received his doctorate in 1979 from Kyoto University in Japan, where he now teaches.

At a news conference hosted by Kyoto University, Kitagawa said he learned about the prize while finishing some work in his classroom. He said he’d been getting many sales calls on his phone recently and so he “answered the phone in a bad mood.”

During the prize announcement, Kitagawa said that he was “surprised and delighted” at having been selected by the committee.

“I want to share my joy with the other two,” he said of Robson and Yaghi.

Yaghi received his doctorate from the University of Illinois Urbana-Champaign and is a professor at the University of California, Berkeley. Yaghi was born to Palestinian refugees who settled in Jordan, and moved to New York for college, first at Hudson Valley Community College in Troy. He switched to the State University of New York at Albany in 1983.