Stable coordination polymers with linear dependence color tuning and luminescent properties for detection of metal ions and explosives

Abstract

A series of new isostructural lanthanide coordination polymers (Ln-CPs), {[Ln(HL)(H2O)2]·(H2O)2}n [Ln = Eu (1), Tb (2), Gd (3), Sm (4), Dy (5), Nd (6), Pr (7) and Er (8), H4L = (1,1ʹ:3ʹ,1ʹʹ-terphenyl)-3,3ʹʹ,5,5ʹʹ-tetracarboxylic acid], were synthesized by using a solvothermal method. Single crystal X-ray diffraction analysis revealed that 1–8 featured (3, 6)-connected layered frameworks with the extended point symbol of {415·66}. The compounds exhibited a variety of luminescence properties including ligand-centred fluorescence, metal-centred 4f–4f emission in both visible and near-infrared ranges. By adjusting the relative ratios of luminescent components in the well-defined host framework, a series of co-doped Ln-CPs {[LnxLn′1-x(HL)(H2O)2]·(H2O)2}n with a linear dependence of color tuning emissions were fabricated. Moreover, 1 and 2 showed thermal stability up to 400 °C and exhibited chemical stability in acid/alkali solutions and different water/ethanol solutions, which render them a promising future for sensing. 1 and 2 can serve as dual-functional materials for sensing metal ions and explosives. Alternatively, 2 displayed excellent recyclable behaviors and can be recycled at least 10 times for sensing Fe3+ and Cr2O72− effectively. The minimum detection limits of Fe3+ and Cr2O72− located in micro molar concentrations (0.28 μmol L−1 and 0.36 μmol L−1), and the quenching constants Ksv were 3.7 × 105 L mol−1 and 3.8 × 105 L·mol−1for Fe3+ and Cr2O72−, respectively.