Synthesis and Structure of an Aqueous Stable Europium-Based Metal–Organic Framework with Ratiometric Fluorescence Sensing for Phosphate and Luminescence Quenching for Salicylaldehyde

An aqueous stable europium-based metal-organic framework with properties of ratiometric fluorescence sensing, namely, {[(CH3)2NH2][Eu(TCPB)(H2O)2]·DMF}n (Eu-MOF; H4TCPB = 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene), was synthesized under solvothermal conditions and structurally characterized. Crystal structure analysis shows that Eu-MOF is a three-dimensional porous crystal, in which the EuIII ion is an eight-coordinate square inverse prism with eight oxygen atoms. Fluorescence measurements show that Eu-MOF exhibits characteristic emission of the EuIII ion and ligand. Eu-MOF displays good selectivity and sensitivity as a ratiometric fluorescence sensor for phosphate anions with a low detection limit in Tris-HCl buffer solution. Furthermore, Eu-MOF also has a good ability to identify salicylaldehyde through fluorescence quenching with a detection limit of 0.095 ppm. Therefore, it is an excellent fluorescent sensing material for phosphate and organic salicylaldehyde.