A coordination polymer based on tetranuclear Tb3+ clusters exhibiting dual turn-on/off fluorescence sensing of long- and short-chain polyfluoroalkyl substances

Abstract

The well-known environmental concerns associated with perfluoroalkyl substances (PFAS) have prompted authorities to impose bans on long-chain PFAS in various applications. However, the relatively minimal restrictions on short-chain PFAS have led to the significant environmental accumulation of these compounds, raising critical health concerns. Hence, there is an urgent need to develop efficient means of monitoring short-chain PFAS. Herein, we report a novel coordination polymer based on tetranuclear Tb³⁺ clusters, having the formula {Tb(L)(μ₃-OH)(H₂O)₂·3H₂O}_n (1). This polymer is constructed from 5-(5-(4H-1,2,4-triazol-4-yl)pyridin-3-yl)isophthalic acid and a Tb³⁺ salt and functions as a fluorescent sensor for perfluorooctanoic acid (PFOA) and trifluoroacetic acid (TFA) in aqueous systems. This material exhibits remarkable stability in various solvents, attributed to its robust framework. Unlike the majority of sensors reported to date, which selectively monitor single PFAS compounds, this new system demonstrates intriguing turn-on/off fluorescence responses to PFOA and TFA, respectively. Using this coordination polymer, the rapid and highly accurate detection of PFOA and TFA at concentrations as low as 0.017 and 105 nM was demonstrated, driven by ligand-field-mediated emissions. A self-calibrating system was deployed by taking the ratio of the emission intensities from the ligands and the Tb³⁺ centers.