Washington, Feb 15 : Scientists at the UCLA (University of Los Angeles, California) have developed new materials that can successfully isolate and capture carbon dioxide, which contributes to global warming, rising sea levels and the increased acidity of oceans.
The carbon dioxide is captured using a new class of materials called zeolitic imidazolate frameworks, or ZIFs, designed by Omar M. Yaghi and his group from UCL.
ZIFs are porous and chemically robust structures, with large surface areas, that can be heated to high temperatures without decomposition and boiled in water or organic solvents for a week and still remain stable.
Rahul Banerjee, a UCLA postdoctoral research scholar in chemistry and Anh Phan, a UCLA graduate student in chemistry, both of whom work in Yaghi's laboratory, synthesized 25 ZIF crystal structures and demonstrated that three of them have high selectivity for capturing carbon dioxide.
"The selectivity of ZIFs to carbon dioxide is unparalleled by any other material," said Yaghi.
"We can screen and select the one type of molecule we want to capture," added Phan.
According to the researchers, the inside of a ZIF can store gas molecules. Flaps that behave like the chemical equivalent of a revolving door allow certain molecules - in this case, carbon dioxide - to pass through and enter the reservoir while blocking larger molecules or molecules of different shapes.
Banerjee and Phan emptied the pores, creating an open framework. They then subjected the material to streams of gases - carbon dioxide and carbon monoxide, for example, and another stream of carbon dioxide and nitrogen - and were able to capture only the carbon dioxide.
Capturing carbon dioxide selectively using this method can prove to be quite beneficial.
"The capture of carbon dioxide creates cleaner energy," said Yaghi. "ZIFs in a smokestack would trap carbon dioxide in the pores prior to its delivery to its geologic storage space," he added.
Currently, the process of capturing carbon dioxide emissions from power plants involves the use of toxic materials and requires 20 to 30 percent of the plant's energy output.
By contrast, ZIFs can pluck carbon dioxide from other gases that are emitted and can store five times more carbon dioxide than the porous carbon materials that represent the current state-of-art.
"For each liter of ZIF, you can hold 83 liters of carbon dioxide," said Banerjee.