A sponge is a beautiful, simple tool. If we spill something, it can soak up the mess and deliver it to where it’s supposed to go. But on the molecular level, tiny, specially engineered sponges could be used to tackle massive problems far beyond the realm of household spills. A new “super sponge” crystal that opens and closes its pores on command could one day mitigate oil disasters, sequester carbon, or even deliver drugs to specific places within a person’s body.
A sponge that can widen or narrow its pores when activated by humans has particular significance for the oil industry. After the Deepwater Horizon oil rig exploded and gushed 20 million gallons of oil into the Gulf of Mexico, researchers at the University of North Texas and the Oak Ridge National Laboratory demonstrated that certain kinds of crystals–what chemists call metal-organic frameworks–could be used to soak up oil.
“The hydrocarbon industry is enormous, and finding out ways to separate products and make things more pure is big money. It’s a big deal,” says Jason Benedict, an assistant professor of chemistry at the University at Buffalo. “But it’s very hard to do this stuff, because you may have to separate molecules with the teeny-tiniest difference in size. And the answer is you need holes, just the right size, to let the right things through.”
With the chemistry that Benedict and his colleagues are working on, the crystals would act like a chemical filter. Already, the natural gas industry uses this screening technique to separate gas from crude, but typically the crystals are “passive” materials, says Benedict. “You make them, and they get used in a variety of ways. What really motivated me was the idea of taking these extremely passive materials and turn them into active materials,” he says.
Benedict and his colleagues, rather, have designed a crystal that can be activated by UV light and then shape-shift its internal makeup. It could be deployed to pick up and release any number of nano-particles at will, like a fleet of ships picking up and releasing passengers at their destinations.
In addition to cleaning up oil spills, similar tactics could one day be used to deliver cancer drugs directly to the site of a tumor, sequester carbon dioxide from the emissions of a power plant, or even sense chemical changes in bodies or buildings. But there’s still a lot of work to be done. Benedict says that the crystals he’s working with tend to break down easily when they run into water, and he has yet to figure out how to switch off the crystals from their active mode. He’s working on that one.