Multifunctionalized Covalent Organic Frameworks for Broad-Spectrum Extraction and Ultrasensitive Analysis of Per- and Polyfluoroalkyl Substances

Abstract

The contamination of surface and ground water by per-and polyfluoroalkyl substances (PFASs) has become a growing concern, and the structural diversity of PFASs is the major challenge for their ubiquitous applications. Strategies for monitoring coexistent anionic, cationic, and zwitterionic PFASs even at trace levels in aquatic environments are urgently demanded for effective pollution control. Herein, novel amide group and perfluoroalkyl chain-functionalized covalent organic frameworks (COFs) named COF-NH-CO-F9 are successfully synthesized and used for highly efficient extraction of broad-spectrum PFASs, attributing to their unique structure and the multifunctional groups. Under the optimal conditions, a simple and high-sensitivity method is established to quantify 14 PFASs including anionic, cationic, and zwitterionic species by coupling solid-phase microextraction (SPME) with ultrahigh-performance liquid chromatography− triple quadrupole mass spectrometry (UHPLC-MS/MS) for the first time. The established method displays high enrichment factors (EFs) of 66−160, ultrahigh sensitivity with low limits of detection (LODs) of 0.0035−0.18 ng L −1 , a wide linearity of 0.1−2000 ng L −1 with correlation coefficient (R 2 ) ≥0.9925, and satisfactory precision with relative standard deviations (RSDs) ≤11.2%. The excellent performance is validated in real water samples with recoveries of 77.1−108% and RSDs ≤11.4%. This work highlights the potential of rational design of COFs with the desired structure and functionality for the broad-spectrum enrichment and ultrasensitive determination of PFASs in real applications.

Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis

“…COFs as SPME coatings, prepared by physical adhesion, the sol–gel method, in situ growth, and chemical cross-linking, have recently attracted considerable attention for the analysis of organic pollutants, including polycyclic aromatic hydrocarbons [ 94 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 ], phenols [ 97 , 113 , 114 , 115 ], polybrominated diphenyl ethers [ 98 , 100 , 116 , 117 , 118 , 119 , 120 ], polyhalogenated biphenyls [ 99 , 121 , 122 ], pesticides [ 123 , 124 , 125 , 126 , 127 , 128 ], and PFASs [ 129 , 130 , 131 ] in environmental samples. The COF-based coatings used for the extraction of targeted compounds in environmental samples are summarized in Table 2 .…”

“…The use of COFs as SPME coatings for the extraction of PFASs has been proposed as a valid alternative to the use of MOFs, featuring a highly hydrophobic and π electron-rich structure [ 129 , 130 , 131 ]. In this context, a novel dioxin-linked COF (TH-COF) was synthesized by microwave-promoted nucleophilic substitution of 2,3,5,6-tetrafluoro-4-pyridinecarbonitrile with 2,3,6,7,10,11- hexahydroxy triphenylene [ 129 ].…”

“…Method validation resulted in very low LOQs (0.0066–0.015 ng/L), recoveries in the 89.5–105% range, and good precision, with RSDs ≤ 8%, allowing for the ultra-trace analysis of pollutants in river, drinking, and underground water samples: perfluoropentanoic acid and perfluorobutanesulfonic acid were detected only in the river water samples at a concentration of 0.480 ng/L and 0.451 ng/L, respectively. Song and coworkers developed a multifunctionalized COF, featuring an amide group and perfluoroalkyl-chain-functionalized chains (COF-NH-CO-F9), to be used for the extraction of anionic, cationic, and zwitterionic PFASs [ 130 ]. The material was obtained under solvothermal conditions and deposited onto SS wires using silicone elastomer.…”

Linkage Transformations in a Three-Dimensional Covalent Organic Framework for High-Capacity Adsorption of Perfluoroalkyl Substances

“…Researchers have shown that adsorbents with cationic groups − or fluorocarbon chains ,, interact strongly with the respective components of PFAS adsorbates (Figure a). This strategy has borne fruit in the design of PFAS-selective COFs.…”