A breakthrough in carbon capture?

Angus Preston

With the growing acceptance of human induced climate change and global warming, scientists and politicians have been looking at ways to limit greenhouse gas emissions. One of the key gases of concern is carbon dioxide, as when it is released into the atmosphere, it essentially acts like a blanket in trapping reflected heat from the earth’s surface. This has contributed to a global increase in temperatures, and is one of the reasons why 2015 is set to be the hottest year on record! (World Meteorological Organisation)

Back in the 1990s, a scientist named Omar Yaghi discovered metal-organic frameworks, or MOFs. These things may be small but they pack a bit of a punch – some have internal surface areas of up to 10,000 square metres per gram! This massive surface area is perfect for the adsorption of gases such as nitrogen, hydrogen or, in this particular case, carbon dioxide. Essentially, MOFs act as a bit of a scaffold with metal atoms acting as the joints and organic compounds acting as the struts. Depending on the shape of the framework and the metal and organic compounds involved, scientists can better design for the capture of specific gases. However, as with most things in science, it’s not quite as easy as that. In fact, one of the latest developments in carbon capture occurred when Ron Smaldone, a Detroit born scientist, wasn’t even researching MOFs. He was trying to make a dye compound out of sugar and salt when he chanced upon a specific framework design that just so happens to favour carbon dioxide adsorption!

Carbon Capture in action

Now it’s not exactly perfect; the adsorption rate isn’t 100% and the adsorptive density is only about 1,200 square metres per gram.  However, the structure of the scaffold and the uneven charge distribution of the Carbon Dioxide molecule allows this MOF gets on really rather well with CO2, and what’s more is its non-toxic, carbon neutral and even edible (if you really wanted…). (Here’s a Berkeley publication on the matter)

The really nifty part is that we no longer have to use potentially harmful metals that don’t do much good when water is involved, such as copper or cadmium.  All that is required is sugar (grown in a carbon neutral way that takes in COfrom the atmosphere) and salt with some potassium ions, and unlike other carbon capture technologies, it works in real life conditions where water is present and doesn’t need any change in ambient pressure. (Read this magazine article)

What Smaldone now hopes to do is set up a company that can utilize this MOF in car exhausts so that most of the carbon is removed, and when the crystal becomes saturated you just swap it out for a new one.  Then you send the old one off somewhere it can be kept to decompose without releasing COinto the atmosphere (they’re looking at storing them in empty oil wells). (An interview with Ron Smaldone)

Editor: Shreya Singireddy