Synthesis, characterisation and luminescent properties of a new three-dimensional lanthanide trimesate: M((C6H3)–(CO2)3) (M = Y, Ln) or MIL-78

Abstract

A new three-dimensional europium-doped yttrium 1,3,5-benzenetricarboxylate has been obtained under hydrothermal conditions. The structure of MIL-78(Y, Eu) or Y_1−xEu_x((C₆H₃)–(CO₂)₃) (x ∼ 0.024) has been solved from X-ray powder diffraction data (a = 6.941(1) Å, b = 14.700(2) Å, c = 8.488(1) Å, β = 107.73(1)°, V = 824.9(4) ų, space group C2/m (no. 12)). Its structure is built up from chains of edged-sharing eight-coordinated monocapped square antiprism polyhedra and trimesate anions, creating a three-dimensional structure. The same structure is formed by replacing yttrium by a rare-earth element. The thermal behaviour of MIL-78(Y, Eu) has been investigated using TGA and X-ray thermodiffractometry and indicates that MIL-78(Y, Eu) is stable up to 450 °C. The study of the optical properties of samples doped with different rare-earths reveals strong fluorescence under VUV radiation.