At the age of just 15, Omar M. Yaghi (Amman, Jordan, 1965) was sent by his family to study in the United States. He first fell in love with chemistry when looking at drawings of the structure of molecules: “I saw these molecular drawings at school and I was amazed, even though I didn’t know what they were. Later I learned that they were the components of things that we cannot see with our own eyes.”
After obtaining a PhD in Inorganic Chemistry from the University of Illinois at Urbana-Champaign, he began his research and teaching career as an assistant professor at Arizona State University, then moved to the University of Michigan at Ann Arbor as Robert W. Parry Professor of Chemistry, and from there to the University of California, Los Angeles as Christopher S. Foote Professor of Chemistry and Irving and Jean Stone Chair Professor in Physical Science. Since 2012 he has been the James and Neeltje Tretter Chair Professor of Chemistry at the University of California, Berkeley, where he co-leads the Kavli Energy NanoSciences Institute, and the California Research Alliance by BASF.
He also heads the Center for Reticular Materials, at Japan’s National Institute for Materials Science, and the Carbon Capture and Conversion Research Group at King Fahd University of Petroleum and Minerals in Saudi Arabia. From 2011 to 2016 he served as Co-Executive Director of the Molecular and Nanoarchitecture (MANAR) Research Center at the Vietnam National University. He holds 44 patents and has a further 25 patent applications published in the United States.
Today, one of his main ambitions outside research is to fire young people with the same enthusiasm, including those from less advantaged countries: “Above all I am a teacher and a mentor, and I want to see more young people engage in science and in the business of solving the world’s problems. All over the world, in the developing countries too. That is why I am helping to build research centers in these countries, to help young scholars to get into science.”
The BBVA Foundation Frontiers of Knowledge Award in the Basic Sciences category goes, in this tenth edition, to Jordanian-American chemist Omar Yaghi, “for his pioneering work in the conception and synthesis of new crystalline materials, MOFs and COFs, of major impact in science and engineering,” with potential applications that extend to “the capture and storage of carbon dioxide (CO2) and trapping water molecules in air to produce water for drinking.”
Yaghi, Professor of Chemistry at the University of California, Berkeley (United States), created these materials using a chemistry based on “building bricks” – the jury explains – whose structure responds to a carefully controlled design. This strategy “has led to an exponential growth in the creation of new materials having a diversity previously unknown in chemistry.”
Yaghi himself gave this new field the name of Reticular Chemistry, which he defines as “stitching molecular building blocks into extended structures by strong bonds.” A strategy already being practiced, the jury remarks, “in numerous laboratories in academia and industry worldwide.”
MOFs (metal-organic frameworks) and COFs (covalent organic frameworks) can be thought of as crystalline sponges on a molecular scale: highly porous materials whose pores or cells, of pre-programmable size, form an organized structure. These frameworks unite many of the properties most prized by chemists, among them a considerable capacity to adsorb other compounds, which lodge within their pores, and exceptional versatility and selectivity, with the size of the pore tailored to the target or “guest” compound. In this sense, they operate like purpose-built “molecular sieves.” As Yaghi explains it, if one gram of an MOF material was unfolded into a single atomic-scale sheet, it would extend across the equivalent of sixty tennis courts.
COFs are formed of organic materials, while MOFs combine organic and inorganic materials, specifically metal oxides. In this case, the metal oxides are the “anchors” – to which the molecule to be caught in the sieve adheres – and the organic compounds are the “struts” that join them together into large porous structures. The choice of metal oxide will depend on the molecule to be trapped, while the size of the pore will depend on the organic compound.
This ability to control the final product has long fascinated Yaghi, who created the first such compound in the mid-1990s: “When I was a student,” – he explained on the phone after hearing of the award – “making new materials involved simply mixing stuff together and what you got at the end was what nature gave you, so there wasn’t much control over what came out. But I realized there must be a lot of potential in being able to assemble units together like you would the components of an automobile. It was a dream for me to be able to make materials in that simple, rational way. To have control over what you are creating and being able to tweak it and modify it after you have made it is really quite powerful.”
Yaghi’s dream was the seed that produced the new chemistry now sweeping the world, with hundreds of laboratories eagerly pursuing fresh applications for these porous materials. The new laureate has to date, he says, counted “more than 60,000” varieties of developed MOFs.
He selects three from among the vast array of potential applications. One is carbon dioxide capture: “Carbon capture is very important, and I believe MOFs may be the best materials to do it,” Yaghi affirms. “The difficulty here is to separate CO2 from other gases, including water. MOFs allow us to seek out just CO2 and separate it so that it does not reach the atmosphere.”
The carbon capture techniques currently in use employ toxic compounds, and can consume over 20% of the fuel the plant produces. MOFs, which are synthesized in a simple, environmentally friendly process, are still not ready for industrial deployment for this application, but Yaghi is convinced that the day will come.
He sees as far more imminent the use of molecular sieves to trap water molecules in air – even in dry environments with less than 20% humidity – to deliver liquid water with no other energy input than ambient sunlight. “There is a lot of water in the atmosphere, and the possibility of trapping it would mark a tremendous transformation in arid regions of the world. We have designed MOFs that can collect water in the pores. Then, heated by sunlight, it comes out as liquid water. True water made from the air.” Yaghi recently published a paper in Science discussing just this application.
Another potential application is the storage of hydrogen in far smaller vessels than are now required. Lodging hydrogen molecules in the pores of the material allows more gas to be contained in a smaller volume – counterintuitively, you can fit a lot more hydrogen into a tank full of MOFs than a tank that is empty. According to Yaghi, the technique is still at the preliminary research stage, but represents a direction of promise for developing a clean, hydrogen-based fuel for vehicles.
Yaghi declares himself increasingly convinced that “the design of new materials is one of the most important things we can do to solve the problems facing our planet, like, for instance, by developing clean energy sources.”
At the start of his career, however, his mind was not on applications, but rather on “the quest to create beautiful structures that I could also control.”