Sweet Relief: How Sugar May Help Reverse Climate Change

by Katie Pratt

This is one of those stories that made me go “WOW that’s cool!” I know, I know, I’m a giant nerd. Also, I’m a biologist not a chemist, so I hope I manage to do it justice.

In a paper published in the Journal of the American Chemical Society a couple of weeks ago a multi-national team of chemists showed how a sugary crystal could soak up CO₂ from the atmosphere.

The general principle behind their experiments was not novel. A number of groups have been using porous metal-organic frameworks (MOFs) to specifically remove CO₂from the air, however in all cases the MOFs were either made of petrochemical byproducts or involved the use of toxic chemicals. Obviously neither of these things is good when your ultimate goal is to clean up the planet.

But Jeremiah Gassensmith and friends have generated a carbon-neutral and toxin-free MOF called CD-MOF-2 (not super-catchy). CD-MOF-2 is made up of γ-cyclodextrin; a ring structure comprising eight sugar moieties similar to those found in starch (a.k.a. amylose). Six of these rings are then assembled into a cube-like structure that is able to stably interact with CO₂. Importantly, γ-cyclodextrin is produced microbiologically from starch (i.e. plant material) and the CD-MOF-2 crystal is formed by water, methanol, or ethanol precipitation. Very green.

Well, actually it’s not green…it’s yellow/red. In order to figure out how CD-MOF-2 was able to remove CO₂from the air the authors of this study incorporated a pH indicator into the crystals. When methyl red (for the chemists out there methyl red is a zwitterionic azobenzene-based pH indicator) was diffused into the pores of CD-MOF-2 the crystals formed were yellow. However after to exposure to CO₂they turned red. This suggested that an acidic substance was accumulating, which turned out to be carbonic acid. Furthermore, this process was reversible and the crystals could be reused repeatedly without suffering any “fatigue”.

This discovery will likely lead to the development of novel technologies for the removal of atmospheric carbon dioxide, and therefore represents an ingenious solution to the very real (no matter how hard the GOP tries to convince us otherwise) climate change planet earth is experiencing.

But this is not the first time cyclodextrins have come to the rescue! Hydroxypropyl β-cyclodextrin is the active ingredient in Febreeze, a household essential for those emergency situations when you didn’t quite get around to doing laundry. And for that lovely fresh scent when you did do you laundry you can thank the cyclodextrins in drier sheets that release fragrances when heated.

Cyclodextrins: Keeping the world fresh and cool.

Katie Pratt is a graduate student in Molecular Biology at Brown University. She has a passion for science communication, and in an attempt to bring hardcore biology and medicine to everyone, she blogs jargon-free at www.katiephd.com. Follow her escapades in the lab and online on Twitter.

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About the winner: Carolien is a post-grad student from Stellenbosch University, South Africa. Trying to find ways to use nematodes in orchards as biological control agents and explaining that to people over casual dinner conversations. [Follow Carolien on Twitter]

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