Powder X-Ray Structural Studies And Reference Diffraction Patterns For Three Forms Of Porous Aluminum Terephthalate, Mil-53(A1)

Powder X-ray diffraction patterns for three forms of MIL-53(Al), a metal organic framework (MOF) compound with breathing characteristics, were investigated using the Rietveld refinement method. These three samples are referred to as the MIL-53(Al)(as-syn) (the as synthesized sample), orthorhombic, Pnma, a = 17.064(2) angstrom, b = 6.6069(9) angstrom, c = 12.1636(13) angstrom, V = 1371.3(2) angstrom(3), Z= 4), MIL-53 (Al)(LT-H) (low-temperature hydrated phase, monoclinic P2(1/c), a= 19.4993(8) angstrom, b= 15.2347(6) angstrom, c= 6.5687(3) angstrom, beta = 104.219(4)degrees, V= 1891.55(10) angstrom(3), Z= 8), and MIL-53(Al)(HT-D) (high-temperature dehydrated phase, Imma, a= 6.6324(5) angstrom, b = 16.736(2) angstrom, c = 12.840(2), V= 1425.2(2) angstrom(3), Z= 4). The crystal structures of the "as-syn" sample and the HT-D sample are confirmed to be the commonly adopted ones. However, the structure of the MIL-53(Al)(LT-H) phase is confirmed to be monoclinic with a space group of P2(1/c) instead of the commonly accepted space group Cc, resulting in a cell volume double in size. The structure has two slightly different types of channel. The pore volumes and pore surface area were estimated to be 0.11766 (8) cm(3)/g and 1461.3(10) m(2)/g for MIL-53(Al)(HT-D) (high-temperature dehydrated phase), and 0.08628 (5) cm(3)/g and 1401.6 (10) m(2)/g for MIL-53(Al)(as-syn) phases, respectively. The powder patterns for the MIL-53(Al)(as-syn) and MIL-53(Al)(HT-D) phases are reported in this paper. (C) 2019 International Centre for Diffraction Data.