Structural changes upon dehydration of Pr (III)(H 2O){C 6H 3[sbnd](CO 2) 3} or MIL-81: A new three-dimensional praseodymium 1,2,4-benzenetricarboxylate with a one dimensional inorganic sub-network

Abstract

A new three-dimensional lanthanide(III) tricarboxylate, MIL-81 1 1 MIL for Material Institut Lavoisier. or Pr (III)(H 2O)(C 6H 3 (CO 2) 3) has been obtained under hydrothermal conditions. Its three-dimensional structure, which has been determined using X-ray powder diffraction data, is built-up from edge-sharing chains of nine coordinated praseodymium(III) capped square antiprisms linked through 1,2,4-Benzenetricarboxylate (1,2,4-BTC) moieties. Its thermal behaviour has been investigated using TGA and X-ray thermodiffractometry and reveals that dehydration is followed by an irreversible structural change giving the solid MIL-81ht or Pr (III)(C 6H 3 (CO 2) 3) with both a change in the environment of the rare earth and in the connection mode of the carboxylate. Crystal data for MIL-81: monoclinic space group P 2 1 with a = 10.272 ( 1 ) Å , b = 7.057 ( 1 ) Å , c = 6.232 ( 1 ) Å , β = 93.668 ( 4 ) ° and Z = 2 . Crystal data for MIL-81ht: triclinic space group P-1 with a = 9.864 ( 1 ) Å , b = 7.054 ( 1 ) Å , c = 5.784 ( 1 ) Å , α = 90.862 ( 9 ) ° , β = 92.439 ( 6 ) ° , γ = 91.594 ( 8 ) ° and Z = 2 .