Tetra-Nuclear Cluster-Based Lanthanide Metal–Organic Frameworks as White Phosphor, Information Encryption, Self-Calibrating Thermometers, and Fe²⁺ Sensors

The application of one kind of metal–organic framework (MOF) material used in multiple fields is one of the most interesting research topics. In this work, four new tetra-nuclear cluster-based lanthanide metal–organic frameworks (LnMOFs) [Ln 2 (BTDB) 3 (DMA)(phen)] n (Ln = Tb TbMOF, Eu EuMOF, Gd GdMOF, Tb 1.830 Eu 0.170 Tb,EuMOF, 3,5-bis(trifluoromethyl)-4′,4″-dicarboxytriphenylamine = H 2 BTDB, 1,10-phenanthroline = phen) are obtained based on the ligand of H 2 BTDB that is synthesized in our laboratory, and the precise single-crystal structure of H 2 BTDB is obtained for the first time. The white phosphor was obtained by facilely hybridizing two components of the orange-yellow emission phosphor of Tb,EuMOF and the blue luminescence material of triphenylamine according to the trichromatic theory. At the same time, TbMOF, EuMOF, Tb,EuMOF, and the white phosphor can be used for information encryption, demonstrating their potential application in the field of anti-counterfeiting. Tb,EuMOF is also a multi-mode and self-calibrating thermometer within a broad temperature range of 110–300 K. Further studies show that EuMOF is a rapid response sensor for Fe 2+, with a very low limit of detection of 2.0 nM, which is much lower than the national standards for Fe 2+ (GB 5749-2005, 5.357 μM). It can achieve strong anti-interference detection of Fe 2+ in actual samples of tap water and lake water. In addition, EuMOF can also be made into an easy-to-use sensing device of test paper for real-time and visual sensing of Fe 2+ .