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−.
A cerium (Ce)-doped metal–organic framework composite (Ce/DUT-52) was prepared by using a solvothermal method and was explored as a sorbent for dispersive solid phase extraction (DSPE) of three estrogens (α-estradiol, estrone, and hexestrol) in human urine samples. After doping with Ce(III), Ce/DUT-52 exhibited more attractive features involving a higher specific surface area (774.7 m2 g−1) and zeta potential (31.4 mV), which made it an efficient adsorbent for the separation and enrichment of estrogens. The factors influencing DSPE efficiency such as the adsorbent amount, extraction time, pH, NaCl concentration, elution solvent and elution volume were investigated in detail. Under the evaluated conditions, Ce/DUT-52 showed good reusability (n = 6, RSDs ≤ 4.8%). Notably, the cofunction of electrostatic interaction, hydrophobic interaction, hydrogen bonding and π–π interaction might play major roles between estrogens and Ce/DUT-52. Finally, coupled with high-performance liquid chromatography (HPLC), a fast and sensitive method was established, which provided low limits of detection (1.5–2.0 ng mL−1), wide linear ranges (3–500 ng mL−1) and satisfactory recoveries (79.8–96.1%). The results demonstrated that Ce/DUT-52 had excellent adsorption ability to the targets and the developed method provided an alternative strategy for the determination of trace estrogens or other compounds with similar chemical structures in urine samples.
A dual-emission, ratiometric fluorescence sensor is reported based on a europium(III)-doped metal-organic framework (Eu/DUT-52) that exhibits blue emission from DUT-52 and red emission from Eu³⁺. Notably, we fond that aflatoxin B1 (AFB1) enhances the fluorescence intensity of DUT-52, whereas the Eu³⁺ emission remains essentially unchanged, enabling ratiometric detection with a concentration-dependent color change from pink to purple. We further investigated the origin of this fluorescence enhancement. The ratiometric response provides a detection limit of 3.9 ng mL⁻¹. For field deployment, Eu/DUT-52 was embedded in a hydrogel to form a simple assay kit, and AFB1 was quantified by smartphone-based RGB analysis of fluorescence images, enabling instrument-free readout with a detection limit of 0.04 µg mL⁻¹. The hydrogel sensor shows good selectivity against other mycotoxins and common metal ions with recoveries of 80.59–111.7% in real samples. This work provides a low-cost, recognition-element-free platform for rapid, on-site screening of AFB1. Graphical abstract The alternative text for this image may have been generated using AI.
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