Chemist Omar Yaghi has won the BBVA Foundation Frontiers of Knowledge Award in the Basic Sciences category, for his pioneering work in developing materials that can capture and store carbon dioxide, harvest water from atmospheric vapor in the desert, or produce clean, hydrogen-based fuels.
In the mid-90’s Yaghi – who was born in Jordan, and is currently a researcher at the University of California at Berkeley - pioneered the development of MOFs and COFs - highly porous materials “of a diversity previously unknown in chemistry,” according to the awards jury.
MOFs (Metal Organic fFrameworks) and COFs (Covalent Organic Frameworks) can be thought of as crystalline sponges on a molecular scale, with pores or cells whose size can be defined to meet different needs. These frameworks have many of the properties most prized by chemists, among them a great capacity to absorb other compounds that lodge within their pores.
COFs are made of organic materials, while MOFs combine organic and inorganic materials, specifically metal oxides. 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 used.
To have control over what you are creating and be able to tweak it and modify it after you have made it, is really quite powerful”
This ability to control the final product has long fascinated Yaghi: “When I was a student,” – he explained by 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 be able to tweak it and modify it after you have made it, is really quite powerful.”
A new chemistry for a cleaner planet
Yaghi’s dream was the seed that produced a new chemistry that is now sweeping the world, with hundreds of laboratories eagerly pursuing fresh applications for these porous materials. The chemist has to date, he says, counted “more than 60,000” varieties of developed MOFs.
Among the vast array of potential applications for MOFs and COFs, Yaghi points to three, for their potential to help create a cleaner planet. One is the capture of carbon dioxide. The key issue when capturing carbon lies in separating CO2 from other gases, and from water. “MOFs are capable of extracting only CO2 and separating it, so that it does not reach the atmosphere,” he explains.
All the tests we’ve run in our laboratories have proven that the use of MOFs to capture CO2 is feasible"
Also, the carbon capture techniques currently in use employ toxic compounds and require huge amounts of energy. MOFs, which are synthesized in a simple, environmentally friendly process, are still not ready to be applied for industrial use, but Yaghi is convinced that the day will come. “All the tests we’ve run in our laboratories have proven that the use of MOFs to capture CO2 is feasible, although I can’t predict how long it will take before we can apply it in industry,” he said.
Harvesting water in the desert
An application likely to arrive sooner is the use of molecular sieves to trap water molecules in the air – even in dry environments with less than 20% humidity – to deliver liquid water, using 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,” says Yaghi. “I am sure that in three to five years we will already have a device capable of drawing pure water from the atmosphere.”
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. Although it seems counterintuitive, you can fit a lot more hydrogen into a tank full of MOFs than a tank that is empty. The technique is still at the preliminary research stage, but it represents a promising possibility for developing a clean, hydrogen-based fuel for vehicles.
Helping young, disadvantaged students to pursue a career in science
When he was only 15 years old, Omar M. Yaghi (born in 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.”
I want to see more young people engage in science and in the business of solving the world’s problems
Today, one of his main ambitions is to fire young people with the same enthusiasm, especially those from less advantaged countries: “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.”