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

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)]center dot 3DMF center dot 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 Ln(3+) 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 D-5(0) -> F-7(2) (Eu3+, 614 nm) to D-5(4) -> F-7(5) (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.