Rapid Capture of Per- and Polyfluoroalkyl Substances Using a Self-Assembling Zirconium-Based Metal-Organic Cage

Abstract

Legacy and emerging per-and polyfluoroalkyl substances (PFAS) are widely detected in environmental and human samples because of their widespread use and resistance to degradation. Due to the increasing concern on health impacts of PFAS resulting from exposure to contaminated water, the development of novel materials to capture and remove PFAS from the environment is needed. Here, we present a self-assembling, fluorinated, zirconium-based metal−organic cage (F-ZrMOC) capable of capturing 37 different PFAS species, at an average of 82% removal from a solution that contains 400 ng/mL of each individual PFAS. The F-ZrMOC captured different classes of PFAS within 30 s, including perfluoroalkyl carboxylates, sulfonates, sulfonamides, ethoxylates, and fluorotelomer carboxylates/sulfonates/alcohols from water during in-vial, static, and flow through exposures (in which the F-ZrMOC is used as a solid phase extraction sorbent). Removal efficiency is higher for PFAS with chain lengths of seven carbons or higher; the presence of complex matrices such as untreated wastewater and groundwater samples did not significantly reduce the removal efficiencies for PFAS. The F-ZrMOC was characterized using 1 H and 19 F nuclear magnetic resonance (NMR) spectroscopy, and the stoichiometry of the synthesized cage was confirmed using Fourier transform-ion cyclotron resonance mass spectrometry. The surface area and pore size of F-ZrMOC were further determined by N 2 and CO 2 sorption measurements. 19 F-NMR spectroscopy revealed that solvent plays an important role in the capture of PFAS; once the cages are in contact with methanol solution, captured PFAS are released.