A Dual-Functional Luminescent MOF Sensor for Phenylmethanol Molecule and Tb³⁺ Cation

A highly luminescent porous metal-organic framework Cd₃(L)_2.5(4-PTZ)(DMF)₃, labeled as NBU-9, has been designedly synthesized based on Cd(NO₃)₂·4H₂O and mixed ligands of 4-(1 H-tetrazol-5-yl)pyridine (4-HPTZ) with N-coordinated sites and thiophene-2,5-dicarboxylic acid (H₂L) with heteroatomic (S) ring and carboxylate groups in N, N-dimethylformamide (DMF) at 100 °C for 3 days. The interesting result is that this compound NBU-9 can be also obtained via the mixed raw materials of Cd(NO₃)₂·4H₂O, 4-cyanopyridine, NaN₃, and H₂L under solvothermal condition at a higher temperature of 140 °C for 3 days, involving in situ ligand synthesis of 4-HPTZ. Its structure was indentified by single-crystal X-ray study, powder X-ray diffraction, element analysis, and TGA results. Structural analysis shows that the three-dimensional framework of NBU-9 contains cubic channels of 9.59 × 10.26 Ų covered by a large number of open S- and O-coordinated sites and can be simplified into a 8-connected uninodal eca net with high potential solvent accessible volumes of 34.1%. Its luminescent properties demonstrate that NBU-9 as a multifunctional sensory material realizes the selective detection for the phenylmethanol molecule on the basis of fluorescence quenching mechanism and effectively sensitizing the visible emitting of the Tb³⁺ cation based on luminescence enhancement.