The science of global warming is complex and the conclusions can be a little inconsistent. One thing that is certain, however, is that humans are adding vast amounts of carbon dioxide (a greenhouse gas) to the environment every year. The fumes from coal-fired power plants as well as the byproducts from gasoline combustion are rich in carbon dioxide gas. Whether or not this gas is causing global warming is a little besides the point. We, as a species, cannot afford to flagrantly waste our natural resources. Our society is based upon the production and consumption of carbon-containing molecules. Carbon dioxide contains carbon atoms, and is therefore one of our richest supplies of starting material for all of our organic syntheses. Simply venting this resource into the atmosphere instead of trying to harness it in some way is probably not the best choice.
With that in mind, I was excited to read a recent article in the journal Chemical Communications that outlined a method for recycling this abundant carbon source. Carbon dioxide is, unfortunately, not very reactive. The number of chemical reactions that it undergoes are limited. One way to circumvent this problem is to utilize a catalyst. Catalysts lower the activation energy required for reactions to proceed, and are extremely powerful. A chemical reaction which may take decades to complete may be finished in seconds in the presence of the correct catalyst. Chemists from German disclosed in the journal article that they had developed a brand new catalyst from a combination of zinc and lithium metals; this catalyst could be useful for addressing the carbion dioxide problem.
The structure of the catalyst is quite special and unique. The zinc and lithium atoms combine with oxygen and small snippets of organic molecules to form a three-dimensional cube. Cubic structures are encountered in organic chemistry, but they’re pretty rare. This cubic catalyst combines carbon monoxide and hydrogen gas to produce a chemical called formic acid, which is the simplest of the organic carboxylic acids and is a valuable starting material for all types of interesting compounds. Unlike carbon dioxide, formic acid is very reactive and so by transforming carbon dioxide into the acid, all of the reactions from that point onwards are very easy.
These heterobimetallic cubane catalysts are exciting news for the chemical industry. We have a virtually limitless supply of carbon dioxide. Every day, tons of it are pumped into the atmosphere by engines and factories. Chemists are no different from any other craftsman: free building materials are always welcome. The fact that we have so much carbon dioxide means that, even with a somewhat expensive catalyst, the conversion into formic acid is economically attractive. The reaction only takes minutes to complete – hydride transfers are usually fast – and so sizable quantities of formic acid could be produced every day. Not only is it the correct environmental decision, as the carbon dioxide is not simply dumped in the atmosphere, but it’s a smart monetary gamble for the chemical industries as well. Producers of the formic acid will find no shortage of buyers for this valuable material. This article is a worthwhile read as it gives you an idea of some of the real-world motivations behind complicated chemical research.
The source of this article can be found at: http://www.rsc.org/Publishing/Journals/CC/article.asp?doi=b714806b
