Lanthanide metal−organic frameworks based on planar π-conjugated ligands for white light emission, temperature and chemical sensing

Abstract

Two stable three-dimensional lanthanide metal-organic frameworks, Ln-MOFs of [M2O(BDCPO)1.5(H2O)7]·2H2O (Eu for CUST-621, Tb for CUST-622) are successfully constructed using π-electron riched ligand N,N′-bis(2,4-dicarboxyphenyl)-oxalamide (H6BDCPO) and Eu and Tb metal ions under solvothermal conditions. The appropriate chromophores in ligands can effectively sensitize Ln3+ ions, resulting in luminescence emission. The crystal structures are determined by single X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, infrared spectrophotometer and luminescence measurements. Triple emission centers are successfully designed and realized the solid-state white light (SSWL) performance, whose CIE coordinates are close to ideal white light (0.32, 0.33). Furthermore, the temperature sensitivity tests indicate that the two materials can be used to sense the temperature in the range of 303–423 K with remarkable color change. The maximum sensitivity are 6.86% K−1 and 7.73% K−1 at 423 K, respectively. Moreover, CUST-621 and CUST-622 can be used as multi-responsive luminescence sensors to Fe3+ and Cr2O72−, with high sensitivity, long-time stability and remarkable selectivity with resistance to interference from other ions. This work supply a general way to construct Ln-MOFs materials for multifunctional luminescence properties for sensing fields.