Covalent organic frameworks (COFs) are promising materials for applications like water purification and gas separation. But COFs tend to be brittle and difficult to work with, so researchers have explored a variety of ways to improve their mechanical properties. Now, researchers at Nankai University, Tianjin University, and the University of South Florida have incorporated polymers into the COF structure, giving the material improved strength and flexibility (ACS Cent. Sci. 2019, DOI: 10.1021/acscentsci.9b00212). The material also bends when it adsorbs ethanol vapors. The researchers used these qualities to get a small doll made with the material to perform sit-ups.