A multifunctional metal-organic framework showing excellent fluorescence sensing and sensitization

Luminescent metal-organic frameworks (LMOFs) have been widely used as sensors and sensitizers for some chemical species due to their functional sites and porosity. In this work, a new metal-organic frameworks, [Cd2(H2L)2(H2O)5]. 5H2O.2DMF (1), has been successfully synthesized using 2,5-bis-(3,5-dicarboxyphenyl)thiopheneamide (H4L) under solvothermal condition. Single crystal X-ray diffraction analysis reveals that 1 has a basic tetranuclear unit, in which H4L is incompletely deprotonated. Furthermore, the basic tetranuclear units are connected into 3D supramolecular network by hydrogen bonds and π-π stacking interactions. As expected, the participation of the fluorescent ligand H4L endows 1 with a strong fluorescence emission. Thus, we systematically explored the fluorescence sensing responses of 1 to small organic molecules and metal ions. Notably, complex 1 can act as a potential multifunctional fluorescence material for sensing of p-nitroaniline and Fe3+ ion with high stability, selectivity and sensitivity. In addition, complex 1 also protects Eu3+ cations from solvent quenching and sensitizes encapsulated Eu3+ hydrates emitting in the UV-vis region. This work highlights the practical application of luminescent MOFs as sensors and sensitizers.