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Wei Zhang, an assistant professor in the Department of Chemistry and Biochemistry at the �鶹ӰԺ, has won a prestigious Sloan Research Fellowship.

Awarded annually since 1955, the fellowships are given to early career scientists and scholars whose achievements and potential identify them as rising stars and as the next generation of scientific leaders. The 2013 fellowships were awarded to 126 U.S. and Canadian researchers.

“The Sloan Research Fellows are the best of the best among young scientists,” said Paul L. Joskow, president of the Alfred P. Sloan Foundation.

“If you want to know where the next big scientific breakthrough will come from, look to these extraordinary men and women. The foundation is proud to support them during this pivotal stage of their careers.”

Zhang’s research group is developing novel materials with potential applications in solar-energy conversion, chemical sensing and catalysis and gas separation and storage. The gas-separation work could lead to new and improved mechanisms of “clean coal”—or carbon capture and sequestration—in which carbon dioxide is captured and pumped underground, where it can become inert.

Finding the most efficient means of capturing carbon emitted by burning coal will be important for some time to come, Zhang said. Even if the world vastly scales up its use of renewable energy, it will need to rely on fossil fuels during the transition, he said.

Zhang’s group has pioneered the development of very rigid, purely organic, three-dimensional “cage molecules,” which act as gas-catching and storage material.

“Some people compare our material to Legos,” Zhang said. “These compounds have very good selectivity in adsorption of CO2 or other gas molecules over nitrogen.”

Zhang said the development of selective molecular cages is “very exciting” because two primary gases in, say, coal-fired electric plants are CO2 and nitrogen. “If people can realize selective adsorption or permeation of CO2, to remove the CO2 from the flue-gas stream, that would be a huge deal. That would be really big.”

Technology based on Zhang’s line of research, if developed and deployed, would differ from the current method of carbon capture and sequestration, which uses liquid amine compounds, derived from ammonia.

Capturing carbon dioxide with a liquid amine is quite efficient, Zhang noted. It is also energy-intensive. “But the big issue is how you can regenerate the amine for recycled use, because it’s not feasible to dispose tons of amine compounds.”

To regenerate the amine compounds, heat is applied, thereby releasing the CO2 and allowing the amine to be reused. This process requires a lot of energy and releases toxins such as nitrosamines and formaldehyde.

That’s why researchers like Zhang are investigating stable molecular cage compounds that would trap CO2 or other gases. Working with Richard Noble, professor of chemical and biological engineering at CU-�鶹ӰԺ, Zhang’s research group is striving to weave the CO2-collecting cage compounds into membranes.

“That would be more ecologically friendly,” Zhang said. The aim would be to have coal-plant flue gas pass through a sequence of membranes, separating nearly all of the CO2 from N2.

Zhang said the goal is to have cage-integrated membrane materials that can be highly selective for, say, CO2, also with high permeability. “That would be a home run.”

The cage-compound membrane system also holds promise because it is chemically stable even at high temperatures.

The gas molecules’ interaction with cage compounds is weak, meaning it would relatively easy to regenerate the cage compounds for recycle use. Once the CO2 is captured by the cage compounds, the carbon could be removed with a vacuum, Zhang said.

A set of cage compounds held together in a membrane would then be used over and over.

The Zhang group has developed a new catalytic method that allows the group to prepare the cage compounds very efficiently.

Scientists have been studying cage compounds for a few decades, Zhang said. But building the CO2-grabbing compounds is “not trivial,” so the challenge is finding ways of producing them efficiently. “We don’t want to spend a couple years preparing one molecule.”

The Zhang group has explored ways to build the cage molecules to target other gases. While one cage compound can target CO2, another could target oxygen, thus making it easier and cheaper to extract oxygen from the atmosphere.

The Sloan Research Fellowship winners were selected through close cooperation with the scientific community. To qualify, candidates must first be nominated by fellow scientists and are subsequently selected by an independent panel of senior scholars. Fellows receive $50,000 to be used to further their research.

Wei earned his Ph.D. in chemistry from the University of Illinois at Urbana-Champaign in 2005 and joined the CU-�鶹ӰԺ faculty in 2008. He won the National Science Foundation’s CAREER Award for early career scientists in 2011.

Also that year, the CU Technology Transfer Office named Wei one of CU-�鶹ӰԺ’s New Inventors of the Year. He is listed as co-inventor on seven patents registered with the U.S. Patent and Trademark Office.