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 × 10 4 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.