HOUSTON, TX — Researchers at Rice University have created multipurpose, light, and highly absorbent aerogels.
The sponge-like materials are synthesized from covalent organic frameworks (COFs) that are typically powders. With this new synthesizing technique, COF aerogels can be made in any form at any size, limited only by the reaction chamber.
Chemical and biomolecular engineer Rafael Verduzco and Rice graduate students Dongyang Zhu and Yifan Zhu and their colleagues at Rice’s Brown School of Engineering have discovered that the powdery crystal structures with strong molecular bonds can form a porous aerogel for use as a custom membrane in batteries or other devices or as an absorbent to remove pollutants from the environment.
“The big advantage of polymers is that you can dissolve them in a solvent, you can spray coat, spin coat, and dip coat them, and they’re easy and cheap to work with, but COFs are not. They’re an insoluble powder and hard to do anything with, but they are really promising for applications because you can design or engineer them almost any way you want on the molecular level. They’re like Lego blocks and you can pick the molecular shapes, sizes, and characteristics you’d like to include in the final material,” Verduzco said.
“We were looking for ways to make COFs easier to work with, more like polymers, and we found that under particular reaction conditions they would form a gel. When you extract the solvent, you get this very light foam or aerogel,” he continued.
To create the aerogels, COF monomers, a solvent, and a catalyst are mixed and heated to 176 degrees Fahrenheit. They will then form a uniform gel. The gel is then washed and dried to remove the solvent leaves behind the scaffold-like aerogel with pores between 20 and 100 microns.
According to Verduzco, COF aerogels could be a valuable addition to industrial absorbents currently in use for remediation as their porous structures can be customized.
The aerogels can also mimic biological membranes. “Nobody’s figured out how to efficiently separate a mixture of ions or molecules that are about the same size and shape, but with this class of materials, we can precisely control the pore sizes and shapes,” Verduzco said.
“Biological membranes separate ions of the same size and charge through small changes in pore functionality that preferentially bind one ion or the other. I think we can start to make synthetic materials that have similar properties,” he continued.