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

摘要

A flexible tripodal polyaromatic acid (4,4',4"-(((2,4,6-trimethylbenzene-1,3,5-triyl)-tris(methylene))-tris-(oxy))tribenzoic acid, H_3TCM) was used to adapt the coordination sites of lanthanide ions for the construction of microporous lanthanide-organic frameworks (LOFs) [LnTCM(H_2O)_2]·3DMF·H_2O (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 (Eu~(3+) and Tb~(3+)) which results in high-efficient resonance energy transfer from TCM to lanthanide ions. Moreover, the mixed Eu_xTb_(1-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 Ln~(3+) ions and the energy allocation between Eu~(3+) and Tb~(3+) ions in the luminescence spectra. We demonstrate that the Eu_xTb_(1-x)-TCM sensor has the capability of decoding different volatile organic molecules (VOMs) with a clearly differentiable and unique emission intensity ratio of ~5D_0 → ~7F_2 (Eu~(3+), 614 nm) to ~5D_4 →~7F_5 (Tb~(3+), 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 Eu_xTb_(1-x)-TCM platform, which has great potential for practical applications.