Polycrystalline Covalent Organic Framework Films Function as Adsorbents, Not Membranes

Covalent organic framework (COF) materials are a class of crystalline, permanently porous polymers with a regular reticular architecture. The stable covalent bonds and tunable pore sizes seem to optimally position COFs as functional membranes for energy-efficient separations, with intuitive structure-property relationships. Thick, polycrystalline COF films have been reported to separate dyes, salts, bacteria, and nanoparticles on the basis of size-selective transport through ordered pores. This talk will highlight a paired experimental and computational approach that identified adsorption as the primary mechanism driving molecular separations in these state-of-the-art films, rather than size-selective sieving. Our results suggest that separations based on differential transport through ordered COF pores remain an important yet unrealized frontier. Efforts to improve the routine materials quality of COF films, critical towards the goal of realizing a size-sieving membrane, are ongoing