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Metal–organic frameworks (MOFs) are a unique class of multifunctional hybrid crystals that have been successfully utilized in diverse ranges of applications. However, since MOFs are prone to aqueous degradation, the development of stable luminescent MOF platforms in aqueous media is still a huge challenge. Here, a novel dual-ligand Eu3+/DUT-52-COOH composite is prepared based on the luminescent DUT-52 prototype structure via a dual-ligand strategy and a post-synthetic modification (PSM) method. The functionalized Eu3+/DUT-52-COOH material exhibits dual emission and good photothermal stability in aqueous media. Thus, Eu3+/DUT-52-COOH is developed as a ratiometric luminescent sensor to achieve highly selective and sensitive detection of Cu2+ and Cr2O72− in aqueous solutions and has a low detection limit of 3.43 μM and 25.7 nM, respectively. This work is one of the few cases of detecting Cu2+ and Cr2O72− in aqueous media based on a DUT-52, and the detection signals can be observed by the bare eye without using sophisticated analytical instruments. The possible sensing mechanism is discussed in detail. The results obtained in this project may provide broad prospects for developing smart sensing systems to accomplish highly efficient, easily operable and quantitative intelligent recognition of Cu2+ and Cr2O72−. [ABSTRACT FROM AUTHOR]

Excitation dependent luminescent materials, which have attracted significant scientific attention in the field of information security owing to information storage and luminescence properties. However, it remains a formidable challenge in developing excitation dependent luminescent materials with a simple synthesis method and predictably modulated luminescent outputs. Herein, a novel Ln3+/Fluorescent dyes@MOFs strategy is developed to generate excitation dependent continuous color-changing luminescent materials via a hydrothermal method and post-synthetic modification (PSM), based on metal-organic frameworks (MOFs) matrix doped with lanthanide cations and fluorescent dyes encapsulated into the lanthanide MOFs. The continuous proportional emission of mixed luminescence appeared within a single matrix in response to the different excitation wavelength and the proportional emission control (PEC) mechanism between the two luminescent centers is proposed. In addition, the photoluminescence platform demonstrates a distinct security method based on covert color that are controlled by distinct excitation wavelengths and excellent luminescence stability have also been verified in these new materials. • Ln3+/Hoc@UIO-66(DPA) achieve excitation wavelength-dependent continuous color-tunable luminescence in a single mixture. • Proportional emission control (PEC) mechanism is proposed. • Ln3+/Hoc@UIO-66(DPA) (Ln = Eu, Tb) materials have potential applications in the field of anticounterfeiting. • The materials are acid and alkali resistant, have high thermal stability, and can be multi-functional luminescent. [ABSTRACT FROM AUTHOR]

Luminescent dye molecules have attracted enormous research interest, whereas, there are inherent drawbacks that limit their utilization across a broad variety of fields. Herein, a novel dual-luminescent carboxylic acid functionalization Eu3+/Hoc@UIO-66(H 3 BTC) (Hoc = 7-hydroxycoumarin) was prepared by introducing luminescent dye molecules (Hoc) into the UiO-66-type dual-ligand metal−organic frameworks (MOFs) utilize the encapsulation approach and postsynthetic modification (PSM). UIO-66(H 3 BTC) was constructed using 1,4-dicarboxybenzene (TPA) as the first ligand, which can restrict the aggregation-induced quenching of Hoc dyes and maintains the Hoc dyes stably included after preparation. 1,3,5-benzenetricar boxylic acid (H 3 BTC) was used as a second ligand to sensitize Eu3+ ions for the antenna effect emission and provide detection sites. Eu3+/Hoc@UIO-66(H 3 BTC) material possesses blue luminescence from Hoc molecules as well as red luminescence from Eu3+ when irradiated by UV lamp, which can be used for ratiometric luminescence detection of Cu2+/Fe3+ through reference to the intensity ratios of two emitting peaks. Eu3+/Hoc@MOFs(H 3 BTC) as a luminescence sensor, displays an ultrahigh sensitivity (Cu2+:4.58 μM, Fe3+:18 μM), strong ant-interference ability, and fast response for detecting analytes. This project demonstrates that the dual-ligand Zr-based MOFs and luminescence dyes offers a novel ratiometric luminescence detection platform for heavy metal ions visible identification. • MOFs includes free –COOH groups that can sensitize Eu3+ ions to realize luminescence and provide site-specific assays. • Eu3+/Hoc@UIO-66(H 3 BTC) overcome (ACQ) effects to encapsulate Hoc dye molecule luminescence. • The advantages of dye encapsulation for detection are proven, with dual emission improving sensitivity. • The ratiometric sensor possess a wide linear concentration range, low LOD and visible detection. [ABSTRACT FROM AUTHOR]