Synthesis, structure and thermal properties of a novel 3D aluminophosphateUiO-26

The synthesis of a novel 3D aluminophosphate is described. The thermal prop erties of the material were investigated, and the existence of three high-t emperature variants was revealed. The crystal structures of the as-synthesi zed material (UiO-26-as) and the material existing around 250 degreesC (UiO -26-250) were solved from powder X-ray diffraction data. UiO-26-as with the composition [Al4O(PO4)(4)(H2O)](2-)[NH3(CH2)(3)NH3](2+) crystallizes in th e monoclinic space group P2(1)/c (no. 14) with a = 19.1912(5), b = 9.3470(2 ), c = 9,6375(2) Angstrom and beta = 92.709(2)degrees. It exhibits a 3D ope n framework consisting of connections by PO4 tetrahedra with AlO4 tetrahedr a, AlO5 trigonal bipyramids and AlO5(H2O) octahedra forming two types of la yers stacked along [100] and connected by Al-O-P bondings. The structure po ssesses a 1D 10-ring channel system running along [001], in which doubly pr otonated 1,3-diaminopropane molecules are located. UiO26-250 with the compo sition [Al4O(PO4)(4)](2-)[NH3(CH2)(3)NH3](2+) crystallizes in the monoclini c space group P2(1)/c with a = 19.2491(4), b = 9.27497(20), c = 9.70189(20) Angstrom and beta = 93.7929(17)degrees. The transformation to UiO-26-250 i nvolves removal of the water molecule which originally is coordinated to al uminum. The rest of the structure remains virtually unchanged. The crystal structures of the two other variants existing around 400 (UiO-26-400) and 6 00 degreesC (UiO-26-600) remain unknown. (C) 2000 Elsevier Science B.V. All rights reserved.