2D Lanthanide Coordination Polymers: Synthesis, Structure, Luminescent Properties, and Ratiometric Sensing Application in the Hydrostable PMMA-Doped Hybrid Films

Abstract

Three Ln III coordination polymers [LnL(NO 3 ) 3 ] n • 2C 4 H 8 O 2 (LnL, Ln = Nd, NdL; Eu, EuL; Tb, TbL) based on an asymmetric polymonodentate ligand L, which has abundant branched end groups for chelating Ln III ions and strong light-harvesting ability to sensitize lanthanide luminescence, have been prepared and well characterized. Single-crystal X-ray diffraction studies reveal that they are isomorphic and feature unique undulated two-dimensional (2D) networks where ligand L acted as asymmetric trimonodentate connectors to bind three Ln III ions. Solid-state luminescence determination indicates that TbL emits bright green lights while EuL shows both Eu III -based red emission and L-based blue emission. For EuL, white emission with CIE coordinates of (0.3280, 0.3471) and (0.3441, 0.3236) was obtained upon excitation at 285 and 345 nm, which are close to the NTSC (National Television System(s) Committee) standard value for white emission. In addition, poly(methyl methacrylate) (PMMA) films doped with EuL and TbL (EuL@PMMA and TbL@PMMA) were developed to improve their luminescence performance, thermal stability, and water resistance. With the aid of the PMMA matrix, the emission with the CIE coordinates of (0.3304, 0.3119), which was much closer to the standard white light than that of EuL, resulted when EuL@ PMMA was excited at 296 nm. Prominently, both EuL@PMMA and TbL@PMMA exhibited ratiometric emission responses toward Zn 2+ selectively in water and could in-site detect Zn 2+ to render them as ratio luminescence sensors for Zn 2+ in aqueous solution.

Two luminescent film sensors constructed from new lanthanide coordination polymers for ratiometric detection of Zn2+ and NH3 in water and their white emission properties

“…S5 †. The change trend of IR spectra for the ligand and its complexes is basically the same as that previously reported, 21 indicating that the variation of the terminal group exhibited a negligible impact on the coordination sphere of the Ln 3+ ions.…”

“…S1†) and IR spectra and its lanthanide compounds EuL , TbL and GdL were prepared according to ref. 21, as shown in Scheme 1. The general preparation of lanthanide compounds was as follows: 0.05 mmol Ln(NO 3 ) 3 ·6H 2 O (Ln = Eu, Tb or Gd) in 10 mL of ethyl acetate was added dropwise to a 20 mL ethyl acetate solution containing 40.5 mg (0.05 mmol) of ligand L and a large amount of white precipitation was produced immediately.…”

“…To overcome this, the construction of emissive film materials has been proved to be successful and our previous report indicated that luminescent films with a small amount of luminescent LnCPs doped into a PMMA matrix showed excellent ratiometric sensing ability toward Zn 2+ in aqueous media. 21…”

Metal–organic framework thin films as versatile chemical sensing materials

“…149 Ion Sensors: The rapid, sensitive, and selective detection of ions has utility in a wide range of areas, including prospecting for high-value elements, 90 identifying heavy metal contaminants in water sources, 127,131 and medical diagnostics. 103,132 Please do not adjust margins Please do not adjust margins through binding sites within the MOF, 103,131 or through electrostatic interactions 101 (e.g. the use of a cationic MOF to sense anions and anionic MOFs to sense cations).…”

Dimensional Reduction ofEu‐Based Metal‐OrganicFramework as Catalysts for Oxidation Catalysis of C(sp3)–H Bond

“…[ 26‐30 ] Among the plentiful MOFs family, lanthanide‐based MOFs gradually attracted the attention. It is not only because of their extensive properties, such as luminescence, magnetic and catalytic performance, [ 31‐35 ] but also because lanthanide metals generally have high coordination numbers and adjustable coordination environment, which could make their structures diverse. [ 36‐43 ] Subsequently, the variable and controllable structure also makes Ln‐based MOFs have application potential in heterogeneous catalysis.…”