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

Two stable three-dimensional lanthanide metal-organic frameworks, Ln-MOFs of [M 2 O(BDCPO) 1.5 (H 2 O) 7 ]·2H 2 O (Eu for CUST-621, Tb for CUST-622) are successfully constructed using π-electron riched ligand N,N′-bis(2,4-dicarboxyphenyl)-oxalamide (H 6 BDCPO) and Eu and Tb metal ions under solvothermal conditions. The appropriate chromophores in ligands can effectively sensitize Ln 3+ 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 Fe 3+ and Cr 2 O 7 2− , 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. Eu-MOF and Tb-MOF are used as fluorescence sensors to detect Fe 3+ and Cr 2 O 7 2− in the water environment. The different mass ratios of Eu and Tb are mixed to achieve white light emission. The temperature-sensitive performance experiment were carried out at 303K–423K. The maximum sensitivity of Eu-MOF and Tb-MOF are 6.86% K −1 and 7.73% K −1 at 423 K, respectively. The color of the doped system changes significantly with the change of temperature. • Two isostructural Ln-based MOFs were constructed by π-conjugate system ligands onto its skeleton. • Adjusting the different mass ratios of Eu and Tb achieve the white light emission. • CUST-621 and CUST-622 display excellent temperature sensing performance. • The two fluorescent sensor can detect the analytes in a water environment.