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)(H 2 O) 2 ]·(H 2 O) 2 } n [Ln = Eu ( 1 ), Tb ( 2 ), Gd ( 3 ), Sm ( 4 ), Dy ( 5 ), Nd ( 6 ), Pr ( 7 ) and Er ( 8 ), H 4 L = (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 {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)(H 2 O) 2 ]·(H 2 O) 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 Fe 3+ and Cr 2 O 7 2− effectively. The minimum detection limits of Fe 3+ and Cr 2 O 7 2− located in micro molar concentrations (0.28 μmol L −1 and 0.36 μmol L −1 ), and the quenching constants K sv were 3.7 × 10 5  L mol −1 and 3.8 × 10 5  L·mol −1 for Fe 3+ and Cr 2 O 7 2− , respectively.