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

Abstract

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) [Ln₂(BTDB)₃(DMA)(phen)]_<i>n</i> (Ln = Tb <b>TbMOF</b>, Eu <b>EuMOF</b>, Gd <b>GdMOF</b>, Tb_1.830Eu_0.170 <b>Tb,EuMOF</b>, 3,5-bis(trifluoromethyl)-4',4″-dicarboxytriphenylamine = <b>H₂BTDB</b>, 1,10-phenanthroline = phen) are obtained based on the ligand of <b>H₂BTDB</b> that is synthesized in our laboratory, and the precise single-crystal structure of <b>H₂BTDB</b> is obtained for the first time. The white phosphor was obtained by facilely hybridizing two components of the orange-yellow emission phosphor of <b>Tb,EuMOF</b> and the blue luminescence material of triphenylamine according to the trichromatic theory. At the same time, <b>TbMOF</b>, <b>EuMOF</b>, <b>Tb,EuMOF</b>, and the white phosphor can be used for information encryption, demonstrating their potential application in the field of anti-counterfeiting. <b>Tb,EuMOF</b> is also a multi-mode and self-calibrating thermometer within a broad temperature range of 110-300 K. Further studies show that <b>EuMOF</b> is a rapid response sensor for Fe²⁺, with a very low limit of detection of 2.0 nM, which is much lower than the national standards for Fe²⁺ (GB 5749-2005, 5.357 μM). It can achieve strong anti-interference detection of Fe²⁺ in actual samples of tap water and lake water. In addition, <b>EuMOF</b> can also be made into an easy-to-use sensing device of test paper for real-time and visual sensing of Fe²⁺.