A dual-emissive optical material as a ratiometric fluorescent probe has been demonstrated to be remarkably superior in precise and quantitative analyses. Herein, a novel dual-emissive fluorescent probe Eu-BDC-OH was designed and successfully synthesized using Eu³⁺ and 2-hydroxyterephthalic acid (H₂BDC-OH) at room temperature. Eu-BDC-OH has a three-dimensional interpenetrating network structure with a large number of exposed hydroxyl functional groups, providing abundant active sites for molecular recognition. In particular, the as-obtained Eu-BDC-OH serves as a unique fluorescent probe, and the double emission peaks of both the ligand and Eu³⁺ are completely quenched by Fe³⁺. However, it is worth noting that the dual emissions of Eu-BDC-OH enable the ratiometric detection of Fe²⁺, which leads to an increase in ligand emission and a decrease in Eu³⁺ emission, accompanied by a distinct red to blue color transition. The relative fluorescence intensity ratio (I_{618 nm}/I_{433 nm}) decreased linearly with increasing Fe²⁺ concentration in the 0–50 μM range with a superior detection limit of 0.32 μM. In this work, a fluorescent probe based on a MOF was developed for the recognition of Fe²⁺ and Fe³⁺, providing a promising strategy for the synthesis of novel dual-emission materials by integrating suitable luminescent ligands with lanthanide metal ions.

中文翻译：

---

用于选择性和灵敏检测 Fe3+ 和 Fe2+ 的双发射铕基金属有机框架

作为比率荧光探针的双发射光学材料已被证明在精确和定量分析中具有显着优势。在此，使用 Eu ³⁺和 2-羟基对苯二甲酸 (H ₂ BDC-OH) 在室温下设计并成功合成了一种新型双发射荧光探针 Eu-BDC-OH 。Eu-BDC-OH具有三维互穿网络结构，具有大量暴露的羟基官能团，为分子识别提供了丰富的活性位点。特别是，所获得的 Eu-BDC-OH 作为一种独特的荧光探针，配体和 Eu ³⁺的双发射峰被 Fe ³⁺完全淬灭. 然而，值得注意的是，Eu-BDC-OH 的双重发射使 Fe ²⁺的比率检测成为可能，这导致配体发射增加和 Eu ³⁺发射减少，伴随着明显的红色到蓝色过渡。相对荧光强度比（I _{618 nm} / I _{433 nm}）随着Fe ²⁺浓度在0-50 μM 范围内的增加而线性下降，检测限为0.32 μM。在这项工作中，开发了一种基于 MOF 的荧光探针，用于识别 Fe ²⁺和 Fe ³⁺通过将合适的发光配体与镧系金属离子结合，为合成新型双发射材料提供了一种有前景的策略。