This blog is my attempt to reconnect with the world of chemistry. I have a PhD in Inorganic Chemistry and make a living doing research for a large company in Michigan. As times have changed, that company has changed its focus and I no longer have as much chance to do the basic, fundamental research which I most enjoy. Through this blog, I am hoping to recapture the magic which I felt during my graduate (and undergraduate) days in college. Expect topics on chemistry and alchemy along with some non-chemistry related items which I think might be interesting.

"The chymists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasure among smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I would change places with the Persian King."

Johann Joachim Becher (phlogistonist)
Acta Laboratorii Chymica Monacensis, seu Physica Subterranea, (1669).

Monday, March 3, 2008

Gas Storage Frameworks

Recently I came across an article which describes the antibacterial use of nano-scale silica xerogels to deliver NO (which was stored/adsorbed within the xerogel framework) directly to bacterial cells at infection sites in order to kill the bacteria. According to the report, the relatively unreactive silica does not cause the same problems as other NO delivery methods (such as chemical compounds which react or decompose to generate the NO). Using porous inorganic materials as storage containera for gases is not a new idea. Zeolites, alumino-silicate frameworks with porous structures, have routinely been used in this capacity. By varying the zeolite properties such as the size of the internal channels, the diameters of the pore openings, the type and number of cross channels, and the number of acid sites, zeolites can be made to selectively store molecules of various types. They are often used as hydrocarbon traps, and I’ve used them to adsorb water from organic solvents.

There have recently been several articles promoting the use of new porous framework materials for specific gas storage applications. Chemists at UCLA have been working on ZIFs (zeolitic imidazolate frameworks) as a CO2 storage material. Led by Omar Yaghi, who also invented MOFs (metal organic frameworks) in the 1990s, the team has been busy generating as many structurally different variants as possible and measuring their ability to selectively capture different gas molecules. Their latest material, ZIF-69, is particularly good at holding onto CO2, opening up the possibility of using this material to sequester the CO2 released by powerplants. Perhaps even more intriguing, and an area that I expect to see a lot of work in the future, would be the use of these framework materials as fuel storage devices. Both hydrogen and ammonia (an alternative source of hydrogen) have potential as non-hydrocarbon fuels, but their pressurized storage can be tricky. Designing porous materials which allow the storage of these gases at much lower pressures would have huge benefits. Although the potential is there, this is not a slam dunk by any means. You not only have to develop a material that holds on to the gas molecules efficiently, but which also releases those molecules at the appropriate time with a minimum of energy input. I will be interested to see where this research goes.

No comments: