New 5-Bromoisophthalate and 2,5-Di(pyridin-4-yl)phenol Appended Zn(II) Coordination Polymer as Recoverable Turn-Off–On Photoluminescent Sensor for Hydroxide Anion

Abstract

Coordination polymers (CPs) represent a diversified class of multidimensional materials that serve as luminescent sensors for detecting ions and molecules present in aquatic environment. In this study, a new Zn(II)-based CP, [Zn (BrIP)(DA)·0.3DMF] (1), incorporating 5-bromoisophthalate (BrIP) and 2,5-di(pyridin-4-yl)phenol (DA), is synthesized and characterized. This CP functions as a turn-off photoluminescent sensor for OH⁻ anion detection through the formation of a 1@OH⁻ complex, exhibiting a limit of detection (LOD) of 1.64 × 10⁻⁴ M and a Stern–Volmer constant (K_sv) of 2.62 × 10⁴ M⁻¹. Notably, the emission of 1@OH⁻ is restored in the presence of p-hydroxybenzoic acid (p-HBA). The sensing of ⁻OH and emission restoration of 1 with p-HBA have been explained with theoretical calculations. The selective recovery of the emission response of 1 upon p-HBA addition, in contrast to other phenolic derivatives, is attributed to its higher E_HOMO and reduced steric hindrance compared with other oxidants investigated in this study.