Engineering Photoluminescence of Lanthanide Doped Yttrium-MOF-76 for Volatile Organic Compound Sensing

A set of three-dimensional metal-organic frameworks, named MOF-76, belonging to the tetragonal P4₃22 space group, based on [Y(BTC)(H₂O)](DMF)_1.1 (1,3,5-benzenetricarboxylate) doped with Eu³⁺, Tb³⁺, and Eu³⁺/Tb³⁺ were obtained under solvothermal conditions and fully characterized by powder X-ray diffraction, thermal, and vibrational analyses. In addition, upon UV light excitation (280 nm), all the powdered samples exhibited fine 4f-4f transitions, of which the ⁵D₀ → ⁷F₂ (Eu³⁺) and ⁵D₄ → ⁷F₅ (Tb³⁺) were the most intense ones. All samples were photophysically analyzed by determining the luminescence lifetimes, and their emission colors were quantified by calculating their chromaticities and color purities. Moreover, the intrinsic quantum yield, radiative, and non-radiative constants were calculated and compared to establish a structure-property relationship. Specifically, the Eu/Tb co-doped sample was employed to monitor its hypersensitive emissions in the presence of small volatile organic compounds (VOCs), showing quenching or enhancement of emission in protic and non-protic solvents. Furthermore, DFT calculations were carried out to understand the energy transfer processes between the sensor and the respective analytes. These results are promising for the development of solid-state lighting devices and colorimetric chemical sensors for specific compounds.