Highly sensitive fluorescent sensing and photocatalytic degradation performance of two-dimensional Tb-organic network

A novel tetra-nuclear Tb-organic network, named as [Tb4(2-pyia)6(HAc)0.5(2,2′-bipy) (H2O)4.5]·2,2′-bipy·H2O (1), was synthesized hydrothermally based on 5-(pyridin-2-ylmethoxy) isophthalic acid (H2pyia) and 2,2′-bipyridine (2,2′-bipy) ligands, and characterized by single crystal X-ray diffraction, thermogravimetric (TG) analyses, powder X-ray diffraction (PXRD) and infrared (IR) technology. 1 possesses a two-dimensional network based on the tetra-nuclear inorganic building units, and the π-π stacking interactions between the pyia2− ligands and the guest 2,2′-bipy molecules play an important role in the forming of 3D supramolecular structure. 1 exhibits excellent fluorescent sensing performance for Fe3+ (1.26 × 10−8 mol/L), Cr2O72− (8.1 × 10−7 mol/L), 2,4,6-trinitrophenol (TNP) (2.71 × 10−8 mol/L) and tetracycline (TCT) (2.76 × 10−7 mol/L) in aqueous solution with lower detection concentrations. The sensing mechanisms of 1 were investigated by density functional theory (DFT) calculations, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy, PXRD and fluorescent lifetime analyses. The activated product of 1 was prepared by heating at 255 °C under constant pressure and used to photo-catalytically degrade TCT. Both 1 and the activated one have good photocatalytic degradation performance for TCT with degradation rates of 84.29% and 96.07%, respectively. The photocatalytic mechanisms were discovered by UV–Vis diffuse reflectance spectroscopy and radical trap experiments. The Tb-organic framework might be an excellent multifunctional fluorescent sensor and a good photocatalytic agent for TCT degradation in the future.