Freeze-dried foam sponges up CO2 from the air
Researchers at Rice University have developed a new material that could be used to capture carbon dioxide from the atmosphere. Made from hexagonal-boron nitride (h-BN) and polyvinyl alcohol (PVA), the foam can soak up more than three times its own weight in CO2, before releasing the gas on demand and allowing the spongey substance to be reused.
To make the material, the team took two dimensional sheets of h-BN and freeze dried it, causing it to puff up into a 3D foam. In that state, it's still fairly brittle and dissolves in liquid, so the researchers bolstered it with a bit of PVA. They mixed the glue-like substance in with flakes of h-BN, and when the solution was freeze dried, the h-BN sheets form a lattice pattern that is held together by the PVA.
"Even a very small amount of PVA works," says Chandra Sekhar Tiwary, co-author of the study. "It helps make the foam stiff by gluing the interconnects between the h-BN sheets – and at the same time, it hardly changes the surface area at all."
Simulating the dynamics of the material's molecules, the team found that the foam can adsorb 340 percent of its own weight in CO2, which can then be evaporated out of the sponge. That allows the material to be reused, and according to compression tests, it became stiffer after 2,000 cycles.
Along with being reusable, the researchers say the freeze-drying manufacturing process is simple enough to scale up for production. Eventually the material could find use in air filters, and if the team can develop a way to control the size of the pores, it might also be put to work soaking oil out of water. By adding a layer of a polymer called PDMS, the team found the foam could also form an effective laser shield, which might be useful in shielding biological tissue from lasers.
The research was published in the journal ACS Nano, and the molecular dynamics simulation can be seen in the video below.
Source: Rice University