Metal–Organic Cage-Based Three-Channel Fluorescence Sensor Array for Discriminating Per- and Polyfluoroalkyl Substances in Water

Perfluoroalkyl and polyfluoroalkyl substances (PFASs), as a group of fluorinated persistent organic pollutants, have posed serious environmental and health risks. At present, the development of rapid and sensitive detection technologies for PFASs is of great significance for ensuring human health and sustainable environmental development. In this work, the metal-organic cage NH₂-Zr-MOC was synthesized via the solvothermal method and then functionalized through in situ encapsulation and postsynthetic modification, yielding the fluorinated and amide-functionalized Zr-MOC-NH-CO-F5 and the pH-sensitive RGH@NH₂-Zr-MOC composites. Both composites were used to construct fluorescence sensors, which produced distinct fluorescence enhancement signals depending on different PFAS species due to their varying adsorption affinities. On this basis, a three-channel fluorescent sensor array was constructed, which facilitated precise identification and highly sensitive detection of three PFASs by means of pattern recognition at a concentration of 2 μM, with the lowest detection limit (LOD) for a single PFAS as low as 22 nM. Moreover, the array could effectively identify PFASs in tap water and lake water with high accuracy, reaching 92.5%. Further investigation demonstrated that the synergistic effects of electrostatic attraction, intermolecular interactions, Lewis acid-base coordination, and F-F affinity restricted the conformational rotation of the composites, ultimately contributing to the enhanced fluorescence intensity.