Synthesis of Cd-MOF and Eu3+@Cd-MOF as Multitarget Sensors for Simultaneous Sensing Cr (VI) Anion and 4-NA

Metal–organic frameworks (MOFs) as a kind of sensing material plays an important role for environmental monitoring and human health. In this paper, we prepared a luminescent Cd-MOF: [Cd₂L·4H₂O]·H₂O. (H₄L = 2,5-bis-(3,4-dicarboxy-phenyl)thiophene-amide) under the solvothermal condition. Single crystal X-ray diffraction analysis shows that Cd-MOF has a 2D layer structure, and it exhibits a strong fluorescence emission at 470 nm. The sensing experiment displays Cd-MOF as multitarget probe can selectively detect Cr (VI) anions and 4-nitroaniline (4-NA) with high sensitivity, good anti-interference ability, and good recyclability. In addition, dual-emission Eu³⁺@Cd-MOF was obtained by encapsulating Eu³⁺ ions into Cd-MOF, in which Cd-MOF sensitizes Eu³⁺ ion emission. Accordingly, Eu³⁺@Cd-MOF also acts as multitarget and self-calibrated probe to selectively detect Cr (VI) ions and 4-NA synchronously at the same conditions. However, the changes of fluorescence emissions of Eu³⁺@Cd-MOF toward Cr (VI) ions are different from that of the original Cd-MOF. The possible sensing mechanism be attributed to the competitive energy absorption between Cd-MOF or Eu³⁺@Cd-MOF and the analytes. All the results may provide broad prospects for developing multitarget sensing platform for sensing environment pollutants.