Hydrothermal synthesis, thermal behaviour and structure determination from powder data of a porous three-dimensional europium trimesate: Eu₃(H₂O)(OH)₆[C₆H₃(CO₂)₃]·3H₂O or MIL-63

Abstract

A new three-dimensional microporous europium carboxylate has been obtained under hydrothermal conditions using trimesic acid and its structure solved from X-ray powder diffraction data. MIL-63 or Eu3(H2O)(OH)6[C6H3(CO2)3]·3H2O crystallises in monoclinic symmetry with a = 17.640(1), b = 3.689(2), c = 12.385(1) Å, β = 91.245(1)°, V = 805.74(4) Å3, space group P21 (no 4). Its structure is built up from nine-coordinate monocapped square antiprism europium polyhedra and trimesate anions, creating pillared structures. The inorganic layers of MIL-63 are similar to those of europium hydroxide, but with a periodic oscillation that leaves within the interlayer space two types of pores along the b axis that contain both free and bound water molecules. The thermal behaviour of MIL-63 has been investigated using TGA and X-ray thermodiffractometry, and indicates that MIL-63 is stable up to 723 K and exhibits zeolitic behaviour.