Unusual High Thermal Stability within a Series of Novel Lanthanide TATB Frameworks: Synthesis, Structure, and Properties­ (TATB = 4,4′,4″-s-Triazine-2,4,6-triyl-tribenzoate)

Abstract

A series of multifunctional lanthanide-organic frameworks Ln­(TATB)­(H₂O) (Ln = Y <b>1</b>, Eu <b>2</b>, Gd <b>3</b>, Tb <b>4</b>, Dy <b>5</b>, Ho <b>6</b>, and Er <b>7</b>; TATB = 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoate) with an unprecedented (4,8)-connected topology have been synthesized and characterized. The structures of these compounds were determined by single crystal X-ray diffraction and their thermal stability, sorption, as well as luminescent and magnetic properties were also investigated. Compounds <b>1</b>–<b>7</b> are isomorphic and present an open non-interpenetrated three-dimensional microporous framework constructed by infinite dinuclear-based, rod-shaped lanthanide-carboxylate secondary building units (SBUs) which arranged in nearly mutually perpendicular directions and interwoven by TATB linkers. All these compounds exhibit very high thermal stability and are stable up to 550 °C. The pore characteristics and gas sorption properties of these compounds were studied by experimentally measuring different gases (CO₂, N₂, and H₂) and different solvent molecules (H₂O and CH₃OH). The luminescent properties of compounds <b>1</b>–<b>7</b> in the solid state were investigated. The results show that <b>2</b> and <b>4</b> exhibited relatively high quantum yields and lifetime values, suggesting that they could be good candidates for light-emitting diodes (LEDs) and light applications. The variable-temperature magnetic studies show that the magnetic interaction between the Ln­(III) ions in <b>2</b>–<b>7</b> was mainly due to the antiferromagnetic coupling as well as the depopulation of the Stark levels. The spin–orbit coupling parameter λ for Eu­(III) (472 cm^–1) has been obtained for <b>2</b>. The in-phase and out-phase signals <i>χ′</i>_M<i>T</i> and <i>χ″</i>_M of <b>5</b> exhibit frequency dependence