Post-synthetic functionalization of Zn-CP by Tb3+ ions: a ratiometric luminescent sensor for the ultraviolet filter benzophenone

Abstract

Developing high-accuracy luminescent sensors for detecting emerging environmental pollutants is of great importance and is still a challenge. Utilizing a 4-carboxyphenylphosphonic acid (H₃pbc) ligand, a novel one-dimensional (1D) Zn-based coordination polymer with the formula [Zn₂(Hpbc)₂(2,2′-bipy)(H₂O)]·H₂O (Zn–CP, H₃pbc = 4-HOOCC₆H₄PO₃H₂, 2,2′-bipy = 2,2′-bipyridine) has been hydrothermally synthesized. Each of the 1D chains was linked via π–π stacking interactions and formed a supramolecular framework. Furthermore, due to the existence of uncoordinated –COOH groups, the terbium-functionalized hybrid (Tb³⁺@Zn-CP) was prepared by introducing Tb³⁺ ions into the structure through coordinated postsynthetic modification (PSM). Tb³⁺@Zn-CP shows the characteristic emission of Tb³⁺ ions due to the “antenna effect” of the H₃pbc ligand. Based on the excellent luminescence properties and structural stabilities of Zn-CP and Tb³⁺@Zn-CP, they can be used as highly sensitive and selective luminescent probes of the UV filter BP (benzophenone) depending on multiquenching effects. In addition, their obvious color change can be easily distinguished by the naked eye under ultraviolet light, which was successfully used in the preparation of portable BP test paper. More importantly, Tb³⁺@Zn-CP is the first example of CPs as a ratiometric luminescent sensor for BP. This work provides a novel strategy for the construction of ratiometric luminescent probes of BP-type UVFs through coordinated postsynthetic modification.