Researchers at the University of California, Los Angeles, believe they have found a better way to filter out greenhouse gases from power plants, creating crystal structures that can selectively capture carbon dioxide without the use of toxic chemicals.

CO2 has been captured in the lab using a new class of materials designed by UCLA chemists called zeolitic imidazolate frameworks, or ZIFs.

"Once they trap it, they let the other gases go through," Rahul Banerjee, a UCLA postdoctoral research scholar in chemistry who is working on the project, told Cleantech.com.

He said crystal structures could be potentially very useful to power plants looking to clean up their emissions.

"You can fill this material into a smokestack, filled with all the ZIF, the zeolitic imidazolate material, and put them into that pipeline, and when the gas bubbles through the pipeline, you can trap the carbon dioxide selectively into the ZIF, and then let the other gases pass through."

Take a look at some ZIF structures here >>

Led by UCLA chemistry professor Omar Yaghi, the research received backing from Germany's BASF (OTC: BASFY), the world's largest chemical company, which funded the synthesis of the materials. The U.S. Department of Energy funded the absorption and separation studies of carbon dioxide.

The DOE recently pulled its financing for a much larger carbon capture project, the $1.8 billion FutureGen Alliance, which was to build a coal-fired, near-zero emissions plant in Illinois (see FutureGen goes FutureBust).

The Alliance, made up of 13 energy and mining companies from around the world, was expected to construct a plant that would gasify and store carbon deep underground, as well as produce hydrogen.

Instead of a single demonstration plant, the DOE now plans to fund multiple, 300 megawatt projects across the country.

Banerjee said that currently power plants send their flue gases through an amine solution, which he said is toxic by itself, and requires 20 to 30 percent of a plant's energy output. The amine bonds with the CO2, which can then be removed.

The bonded solution then needs to be heated to release the CO2 for subsequent storage.

The new sponge-like ZIF material is a potentially lower-cost system for carbon capture.

"It just costs you the zinc nitrate, which is pretty cheap and available in any chemical inventory," said Banerjee.

He pointed out that zinc-oxide is a main ingredient in sunscreen, and that imidazoles are active ingredients of histidine, which is a minor acid.

"It's very much non-toxic and very much cost-effective, because here you don't have to do anything significant other than synthesizing the compound."

According to the researchers, the porous ZIF structures can be heated to high temperatures without decomposition, and even boiled in water or organic solvents for a week and still remain stable.

The UCLA team also said the ZIFs can store five times more carbon dioxide than the porous carbon materials that are available today, with each liter of ZIF holding 83 liters of carbon dioxide.

Banerjee said similar structures have been used in hydrogen storage research, and that some scientists have said the structures could have use in catalysis, using the ZIFs as catalysts to speed up various chemical reactions.

"It is very much renewable, because once you fill that stuff with hydrogen or carbon dioxide or whatever, once you are done with that, you release the valve, you remove you're excess gases, or the gas which has been trapped in the material, you can reuse this material again and again and again," he said.

But it will probably take a few years for the crystals to get to the commercial stage.

"What we are doing right now is we are doing it on a laboratory scale, but when you come to the commercial stage it has to be engineered in such a way that people can use it very easily," said Banerjee.

"We would like to make it very simple for the public so that everybody can use it regularly."