The medical application of ultrasound technology to diagnose health issues is well-known. Dr. Daniel Kim uses similar ultrasonic sound waves with much higher power to create pores or cavities in a class of chemical compounds called metal-organic frameworks (MOFs).
The porous nature of these compounds means they can absorb other molecules which gives rise to a number of potential applications.
"This includes in the field of hydrogen gas storage for hydrogen-powered vehicles, removal of harmful gases from the air, separation of molecules, catalysis, and drug delivery," said Kim, a professor in the Auburn University at Montgomery chemistry department.
Kim’s MOFs contain metal ions such as copper or nickel which are attached to organic (carbon-based) molecules and their chemical units can be repeated many times forming polymers.
But it’s the formation of the numerous tiny cavities that provides MOFs with their unique properties. In addition to acting as storage assemblies for substances, some molecules filling the MOFs holes can become more reactive.
“With large cavities in the MOFs, bubbles are created from the high-intensity ultrasonic waves,” explained Kim. And due to a cycle of gas compression and expansion during irradiation, “gas molecules trapped in the bubbles can reach several thousand degrees Celsius and a pressure of a thousand atmospheres. It makes chemical reactions under ultrasound extremely fast – one that might take days to complete can occur in minutes.”
Kim’s work also focuses on the environmental applications. “I have applied ultrasound irradiation to the degradation of pollutants in water.”
A third area of interest is the preparation of new compounds. “As an organic chemist, I am trying to apply the ultrasonic effect to a variety of organic syntheses,” he said.
After completing Bachelors and Masters degrees at Yonsei University in South Korea, Kim continued his graduate studies at Florida International University, Miami.
“My research for the completion of my Ph.D. had two tracks,” he recalled. “One was a synthesis of an unstable organic compound and its structure determination by nuclear magnetic resonance (NMR) spectroscopy. The other was applying ultrasound to the degradation of organic pollutants in water and elucidation of the reaction mechanisms.”
Dr. Kim brings his international research experience to the River Region scientific community.
“AUM has been providing me with opportunities to work with many undergraduate students," he says. "My goal is to nurture their scientific curiosity for their career success.”
Nick Thomas teaches at Auburn University at Montgomery (aum.edu) and has written features, columns, and interviews for over 700 newspapers and magazines (getnickt.com).