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A Luminescent Mixed-Lanthanide-Organic Framework Sensor for Decoding Different Volatile Organic Molecules

Zhan, Chao, Ou, Sha, Zou, Chao, Zhao, Min, Wu, Chuan-De
Analytical chemistry 2014 v.86 no.13 pp. 6648-6653
energy transfer, europium, ions, luminescence, porous media
A flexible tripodal polyaromatic acid (4,4′,4″-(((2,4,6-trimethylbenzene-1,3,5-triyl)-tris(methylene))-tris(oxy))tribenzoic acid, H₃TCM) was used to adapt the coordination sites of lanthanide ions for the construction of microporous lanthanide-organic frameworks (LOFs) [LnTCM(H₂O)₂]·3DMF·H₂O (Ln-TCM; Ln = La, Eu, and/or Tb). In these LOFs, the emission band of TCM matches well with the excitation energy of lanthanide ions (Eu³⁺ and Tb³⁺) which results in high-efficient resonance energy transfer from TCM to lanthanide ions. Moreover, the mixed EuₓTb₁–ₓ–TCM has tunable pores to adapt different induced-fit-type host–guest interactions which can modulate both the energy transfer efficiency from TCM to Ln³⁺ ions and the energy allocation between Eu³⁺ and Tb³⁺ ions in the luminescence spectra. We demonstrate that the EuₓTb₁–ₓ–TCM sensor has the capability of decoding different volatile organic molecules (VOMs) with a clearly differentiable and unique emission intensity ratio of ⁵D₀ → ⁷F₂ (Eu³⁺, 614 nm) to ⁵D₄ → ⁷F₅ (Tb³⁺, 545 nm) transitions for every different VOM. Compared with the traditional absolute emission intensity method, such a self-referencing emission intensity strategy has generated self-calibrating, highly differentiable, and very stable luminescent signals for decoding different VOMs from the unique EuₓTb₁–ₓ–TCM platform, which has great potential for practical applications.