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

A series of new isostructural lanthanide coordination polymers (Ln-CPs), {[Ln(HL)(H2O)(2)] center dot (H2O)(2)}n [Ln = Eu (1), Tb (2), Gd (3), Sm (4), Dy (5), Nd (6), Pr (7) and Er (8), H4L = (1,1':3',1 (2)-terphenyl)-3,3 (2),5,5 (2)-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 {4 (15).6 (6)}. 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 {[Ln(x)Ln'(1-x)(HL)(H2O)(2)] center dot (H2O)(2)}(n) with a linear dependence of color tuning emissions were fabricated. Moreover, 1 and 2 showed thermal stability up to 400 degrees 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 Cr2O7 (2-) effectively. The minimum detection limits of Fe3+ and Cr2O7 (2-) located in micro molar concentrations (0.28 mu mol L-1 and 0.36 mu mol L-1), and the quenching constants K-sv were 3.7 x 10 (5) L mol(-1) and 3.8 x 10 (5) L mol(-1)for Fe3+ and Cr2O7 (2-), respectively.