Design Principles for PFAS Adsorption in Three-Dimensional Covalent Organic Frameworks

Recent concerns over the accumulation of per- and polyfluoroalkyl
substances (PFAS) in surface and groundwater sources have stimulated
research into novel porous materials for selective PFAS adsorption.
Covalent organic frameworks (COFs) represent one of the promising
families of materials for this application. Here, we investigated
the effects of the chemistry and structure of three-dimensional COFs
on the adsorption of perfluorooctanoic acid (PFOA), a commonly seen
PFAS molecule. Through Monte Carlo (MC) simulations, we found that
nitrogen-based COFs tend to show high potential for PFAS adsorption.
We also see that the porosity of the COF pores has a significant effect
on PFOA adsorption, with higher porosity structures exhibiting lower
potential for PFAS adsorption than those with moderate porosity. We
additionally investigated the effects of COF functionalization with
−CF3 and −NH2 functional groups,
showing that both functional groups strengthen interactions between
the PFOA molecule and COF, but may decrease the porosity needed for
effective adsorption of PFOA. For COFs with large enough pores, the
addition of these functional groups can greatly improve the adsorption
of PFOA and could allow for the improved capture of PFAS from aqueous
environments.