Europium metal-organic frameworks as recyclable and selective turn-off fluorescent sensors for aniline detection.

Seven Eu-(H)BDC compounds, [RMI][Eu2 (BDC)3 Cl] (R = ethyl (1), propyl (2), butyl (3), H2 BDC = 1,4-benzenedicarboxylic acid), [EMI]2 [Eu2 (BDC)3 (H2 BDC)Cl2 ] (4), [Eu(BDC)(HCOO)] (5), [Eu(BDC)Cl(H2 O)] (6) and [Eu3 (BDC)4 Cl(H2 O)6 ] (7), were synthesized under ionothermal conditions. Compounds 4 and 6 behave as potential highly selective turn-off fluorescent sensors for aniline, which can be detected in mixtures of aniline with contrast organic amides or alkylbenzenes. Fluorescence quenching can be observed when compounds 4 and 6 mix with the samples containing aniline. Compounds 4 and 6 show basically unchanged emission intensities and rapid response to aniline after ten recycling tests, suggesting that the compounds have high stable recycle repeatabilities.