You may have seen a few articles lately about a nuisance of a chemical called carbon dioxide, namely, that it's the waste product of a number of very common chemical reactions and doesn't itself react with much (other than plants, but that reaction isn't fast or extensive enough to keep up with our current production rate) meaning it accumulates in the environment.
So, we're trying to make sure less of it gets into the environment. One class of methods which you may have heard of is carbon capture and sequestration, where after production it's captured, compressed, and often pumped deep underground—sometimes into retired oil wells, sometimes into the deep ocean, or many other places.
Before it can be stored, however, it has to be captured. Scrubbing can be highly effective at removing CO2 from smokestacks and other concentrated sources, traditionally with amine solutions. Then there was a new discovery about the CO2 absorption of polyethylenimine, which was what caused me to start researching this post.
One of the issues with a reaction that is very effective at grabbing a chemical out of the air is making it let go again. Most of the chemicals that are good at grabbing CO2 are too expensive to use only once. Polyethylenimine is of great interest because it releases the CO2 easily by heating it up, which can let the CO2 be collected in concentrated form for use elsewhere.