The escalating contamination by per-and polyfluoroalkyl substances (PFAS) has become an urgent issue in recent years, and the structural diversity of PFAS is the major challenge for effective pollution control. Herein, we take the intrinsic advantages of squaramide and prepare a new two-dimensional covalent organic framework (FSQ-1) that exhibits broadspectrum PFAS affinity. The tailor-made linker forges hydrogen-bond donors, hydrogen-bond acceptors, and fluorophilic segments into one framework. The obtained material exhibits multipoint and multitype affinity to PFAS with different structures, by which high-efficient and broad-spectrum removal of various PFAS can be simultaneously achieved. Notably, the thermodynamic profiles provided by isothermal titration calorimetry (ITC) experiments further illustrate the underlying mechanism of the broad-spectrum affinity. FSQ-1 can also be applied for efficient PFAS extraction in tracelevel PFAS analysis.
The ubiquity of per-and polyfluoroalkyl substances (PFAS) has become an emerging challenge for modern water treatment and public health. The development of high-performance adsorbents remains at the forefront of PFAS remediation. Covalent organic frameworks (COFs) with structural regularity and task-specific functionality are promising candidates yet have not been fully explored. Herein, cystamine-grafted hollow COF nanospheres (hollow Cys-COF) are synthesized via the hard-template method and functionalized by the thiol-ene "click" reaction. The well-defined hollow structure provides a specific "shell-confined" environment, which ensures sufficient modification in a short period and retains the crystallinity of the original material, circumventing the dilemma between functionality and crystallinity in traditional post-synthetic modification protocols. The as-prepared hollow Cys-COF is highly functionalized and shows remarkable removal performance to various anionic PFAS under environmentally relevant conditions. Twenty kinds of anionic PFAS containing carboxylic, sulfonic, and phosphoric individuals are removed by 90% within several minutes, and a column-test further verified its superior performance under the dynamic situation. An integrated analysis from both experimental results and theoretical simulations provides a mechanistic illustration of how the morphology and functionality can jointly contribute to effective PFAS adsorption. These findings provide a multiscale understanding of high-performance adsorbent design.
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