, , , , James A. Kaduk
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) Å, b=6.6069(9) Å, c= 12.1636(13) Å, V=1371.3(2) Å3, Z=4), MIL- 53(Al)LT (low-temperature phase, monoclinic P21/c, a= 19.4993(8) Å, b= 15.2347(6) Å, c= 6.5687(3) Å , β=104.219(4), V=1891.55(10) Å3, and Z=8), and MIL-53(Al)HT (high-temperature phase, Imma, a= 6.6324(5) Å, b= 16.736(2) Å, c= 12.840(2), V= 1425.2(2) Å3, Z=4). The crystal structures of the as-syn sample and the HT sample are confirmed to be the commonly adopted ones. However, the structure of the MIL-53(Al)LT phase is confirmed to be monoclinic with a space group of P21/c instead of the widely used 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) cm3/g and 1461.3(10) m2/g for MIL-53(Al)HT, and 0.08628 (5) cm3/g and 1401.6 (10) m2/g for MIL-53(Al)as-syn phases, respectively. The crystal structures of the three MIL-53 forms are summarized and the powder patterns for the MIL-53(Al)as-syn and MIL- 53(Al)HT phases are reported in this paper.
MIL-53 structures, MIL-53(Al)as-syn, MIL-53(Al)LT, MIL-53(Al)HT, Powder X-ray Reference patterns, MIL-53 pore size ?