Soaking Up Greenhouse Gases Like A Sponge

How can you safely dispose of an old refrigerator without letting the greenhouse gas Freon, which kept it cool, escape into the atmosphere? There have been a few efforts to address this problem, but so far all of them have fallen short.

Now, though, chemists at the University of Houston (UH) have produced a molecule that spontaneously assembles into a lightweight, spongy substance that can soak up huge quantities of many airborne pollutants.

It's only flaw, it seems, is that the sponge is useless against one of the most common offenders, carbon dioixide, according to Ognjen Miljanic, an associate professor of chemistry at UH and leader of the team that created the new molecule.

Still, Miljanic told UH's News & Events department, many other toxic chemicals per unit of mass pack a stronger greenhouse punch than CO2 by factors of hundreds and even thousands. Among them are Freon in its various forms as well as fluorocarbon, another refrigerant that also can be used as a lubricant. Fluorocarbons are so dangerous that they've been banned in the United States.

"We developed a molecule that self-assembles into a structure that can capture these greenhouse vapors to the tune of 75 percent by weight," Miljanic said. "This molecule could be used to capture Freons from disposed refrigeration systems."

Miljanic and his team report in the journal Nature Communications that the molecule they invented, which is combined with the corrosive, non-metallic gas fluorine, forms a structure containing pores with diameters measuring about 1.6 nanometers, or 1.6 billionths of a meter.

These molecules create the structure spontaneously because, being lined with fluorine atoms, have what Miljanic calls "a high affinity [to combine with] other molecules containing fluorine, such as fluorocarbons and Freons."

Previous attempts to capture greenhouse gas emissions before they pollute the atmosphere also have included spongy materials with pores similar in size to the substance Miljanic and his team have developed. But those materials often were heavy because they didn't use fluorine to coat the molecule but instead included substances that were metallic, contributing to the weight of the sponges.

These earlier attempts also led to sponges that became unstable when exposed to water, and were difficult to process and to recycle. The UH team, though, came up with a substance that, according to Miljanic, is "stable to water and composed from individual molecules held together only by weak interactions."

"This latter feature makes this material lightweight, because there are no metal connectors" coating the molecules, Miljanic said.

What's more, the weak interaction holding the molecules together is another asset of this new material, Miljanic said, because the sponges can be broken apart easily to make them the proper size for a specific use, or simply to recycle them.

One other benefit: If necessary, the sponge can be used in an environment as hot as 536 degrees Fahrenheit.

By Andy Tully of Oilprice.com