A Hexadecacationic Metal–Organic Cage for Anchoring Sulfonates: High‐Order Binding of Di‐ and Trisulfonates and High‐Performance Removal of Perfluorosulfonates from Water

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Abstract
Developing synthetic hosts capable of binding sulfonate anions or sequestering perfluorosulfonates is highly important. In this work, the self‐assembly of a tripyridinium‐tricarboxylate ligand with Cp 2 ZrCl 2 (Cp = η 5 ‐C 5 H 5 ) is reported, yielding a highly cationic tetrahedral cage ( 1 ) engineered with acidic C−H protons. The hexadecacationic cage binds a variety of sulfonate anions with unprecedented charge‐discriminative phenomena: the cage binds monosulfonates in fast exchange on the NMR timescale, while di‐ and multisulfonates exhibit slow‐exchange binding. In particular, high‐capacity complexation of di‐ and trisulfonates by 1 is achieved, with the pronounced case of 1 accommodating three dianions. Molecular modeling suggests the existence of a “Y”‐shaped binding pocket on each edge of tetrahedron 1 (six in total), with each pocket capable of anchoring a guest bearing at least two sulfonate headgroups through electrostatic and hydrogen bonding interactions. Further investigations demonstrate that 1 in solid state is an exceptional adsorbent for perfluorooctane sulfonate (PFOS), with a maximum adsorption capacity of up to 1603 mg g −1 positioning it among the top PFOS adsorbents. Moreover, cage 1 exhibits rapid kinetics, high selectivity, and long‐life cycles in PFOS removal, and also effectively adsorbs shorter perfluorosulfonates.
Funding Information
  • National Natural Science Foundation of China (22201075)
  • National Natural Science Foundation of China (21971069)
  • National Natural Science Foundation of China (22301172)
  • National Natural Science Foundation of China (22501086)

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