Ratiometric fluorescence sensing and colorimetric decoding methanol by a bimetallic lanthanide-organic framework

A bimetallic metal-organic framework (MOF) with a yellow-emission signal has been successfully fabricated by appealing to the lanthanide doping strategy. This MOF could behave as a fluorescent sensor for decoding methanol with an obvious color change and unique emission intensity ratio of Tb3+ ion to Eu3+ ion, both in the solution and vapor state. Good detection reproducibility and fast response could be achieved in this sensor. [Display omitted] •A dual-emitting Eu/Tb bimetallic metal-organic framework was synthesized.•This MOF shows strong emission colour and high fluorescence stability.•A selective enhancement of fluorescence of Tb ion is induced by MeOH.•Ratiometric fluorescent sensing of formaldehyde in both solution and vapor state is performed. Ratiometric fluorescence sensor has drawn much attention due to its decreased environment influence and easy-to-differentiate color and intensity change. In this work, a bimetallic metal-organic framework (MOF), namely {(Me2NH2)[Tb0.9Eu0.1(OBA)2]∙(Hatz)∙(H2O)1.5}n (1, H2OBA = 4,4′-oxybis(benzoate) acid, Hatz = 3-amino-1,2,4-triazole) with a yellow-emission signal has been successfully fabricated by appealing to the lanthanide doping strategy. In this MOF, the emission band of OBA2− ligand matches well with the excitation energy of lanthanide ions (Eu3+ and Tb3+) which leads to high energy transfer from the ligand to the lanthanide ions to provide dual emission peaks for the both Eu3+ and Tb3+ ions. This MOF shows high fluorescence stability with the ratio of its two emission peaks (545 nm and 618 nm) do not change with the change of Ln-MOF sensor concentration used as the merit of ratiometric fluorescence detection. Subsequently, we choose this MOF as a fluorescent sensor for various volatile organic molecules, and the results show that it is capable of decoding methanol with an obvious color change and unique emission intensity ratio of Tb3+ ion to Eu3+ ion, both in the solution and vapor state. Good detection reproducibility and fast response could be achieved in this sensor.