Ryong Ryoo tells Rachel Cooper how he took a risk and became an expert in mesoporous materials

	Ryong Ryoo is professor of chemistry at Korea Advanced Institute of Science and Technology and has been on the Chemical Communications editorial board since 2006. He has received numerous awards and was named Korea's national scientist by the Korean government in 2007.

What first attracted you to science?
In the second year of high school in Korea, students are divided into two groups. One group is taught science and engineering and the other is taught an advanced level of literature (such as English). I belonged to the non-science group, so I never thought I would become a scientist. When I was almost at the end of my high school studies, I realised that my ability was science-based, so I decided to risk taking the entrance exam for science at Seoul National University.

Was this unusual?

This was extremely unusual! It was very risky, but fortunately I succeeded in passing the Seoul exam. At that time, I chose chemical engineering as my major. As a student at high school (before my entrance exam), I didn't know the difference between chemistry and chemical engineering. Chemical engineers could find jobs more easily in Korea at that time, and Korea was one of the world's poorest countries. The income per person per year was only US$1000 until about 30 years ago. Parents wanted their children to be able to find jobs very easily, so my parents wanted me to go into chemical engineering.

What made you choose chemistry as a career?
At university, I liked chemistry much more than chemical engineering so I chose to study chemistry. I took the entrance exam for KAIST [Korea Advanced Institute of Science and Technology], a university that gave special exemption from military service. People graduating from KAIST could instead take a job in industry, a research institute or even in a university, with three years' regular salary. I would never have thought about being a chemist otherwise, as my parents could not afford to pay for my graduate studies. Korea was totally different 30 years ago - ordinary people couldn't think about sending their children to study. It cost too much.

KAIST was established several years before I entered; tuition was free and students got scholarships. So that was my opportunity, my chance. I entered KAIST and I saw many senior students going abroad for study, and I thought, 'yes, this is the way - I like chemistry, and I can do chemistry research very well.'

Which area of chemistry did you work in?
Initially, I chose computational chemistry, calculating thermodynamic properties of liquid helium and other liquids. After working at a national lab, the Korea Atomic Energy Research Institute, for three years, I went to Stanford University for my PhD. There, I chose more practical chemistry - heterogenous catalysis. I learnt about xenon gas NMR, and its use on porous materials, such as zeolites, but I didn't learn how to synthesise porous materials at that time. I returned to Korea after a one-year post-doctoral stay at the University of California, Berkeley and I did the same kind of research as I had done in the US. I used zeolites as supports for platinum. I used xenon NMR, extended X-ray absorption fine structure and other physical tools to characterise porous zeolites and supported metal nanoparticles, at that time called clusters.

What is your favourite piece of research?
At a conference in Japan in 1993, I happened to hear about mesoporous silica MCM-41. I was fascinated by its structure and large pores. I wanted to use the material as a support for metal nanoparticles, but I couldn't obtain it then. Although I knew nothing about the chemistry of silica, I decided to synthesise it in my laboratory. I struggled for several years, and somehow became an expert in mesoporous materials. Because I hadn't been trained how to do it, I used my own ideas and this is what brings the field forwards. In 1999, I published a very important paper on the synthesis of ordered mesoporous carbon, using mesoporous silica as a template. Before that, there were no carbon materials showing ordered porosity, so my synthesis of the first ordered mesoporous carbon, named CMK (carbon metastructure at KAIST), was very surprising. It was the first material to exhibit Bragg X-ray diffraction peaks (due to the structural order) with porosity. People were fascinated by the material; they began to use it and to follow the synthesis. So that was my favourite, and best, work.

What do you see as the most important future applications for mesoporous materials?

These days, I work on zeolites with mesoporosity as well as the inherent microporosity. Microporous materials have pores smaller than two nanometres, and mesoporous materials have pores between two and 50 nanometres. Zeolites have micropores about one nanometre and normally they are synthesised as crystals, with no mesoporosity. However, if you synthesise zeolites with mesopores penetrating the crystals then you make a zeolite with both micropores and mesopores; these are called hierarchical zeolites. The advantage of such hierarchical zeolites is that molecular diffusion can take place very rapidly through large mesopores into small micropores. Without mesopores, the diffusion into micropores is very slow. The consequence of such facile diffusion is that zeolites, in many reactions, show dramatically increased lifetimes when they are used as catalysts. This is a great advantage, as you can continuously operate two or three times longer without catalyst replacement, saving money.

The reason for this improvement is not yet well understood, but we believe that it may be due to the facile diffusion of the reactants and products. I think particularly in the case of the intermediate products, it removes the intermediate or product quickly out of the micropores, so that the deactivation of the catalyst (which is caused by the accumulation of the polymeric carbonaceous species forming by an interaction between intermediate species) is reduced. Hierarchical zeolites show increasing lifetimes in a number of reactions, so I am working on that. I am also trying to further develop the synthesis method for hierarchical zeolites.

If you had to completely change your area of research, which topic would you like to investigate?
I would do research in biology. When I was a child, I enjoyed watching birds and insects, and I liked to grow plants in the garden, so biology was my dream. But somehow, I became a chemist. Biologists couldn't find jobs so easily. I think I could do better in biology, but I think it's too late now.

What do you like to do in your spare time?
I like to watch nature and walk. I also like gardening. I have a garden that is quite big for Korea. I have been constructing it for several years. Next year, I plan to have a house built, but before that, I will finish the garden. I believe that people who love plants and animals are suited to do science.