Synthesis, crystal structure and properties of a novel framework aluminium diphosphonate

We report here the hydrothermal synthesis, crystal structure and properties of the hybrid inorganic-organic framework material Al 2[O 3PC 6H 4PO 3](H 2O) 2F 2·2H 2O which is the seventh member of the group 13 metal diphosphonate framework series of formula M (III) 2[O 3PRPO 3](H 2O) 2F 2. The structure is formed from linear chains of corner-sharing AlO 4F 2 octahedra in which the two fluorine atoms are present in a trans configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the phenylene groups to form a three-dimensional framework structure containing a one-dimensional channel system containing eight non-framework water molecules per unit cell. The framework structure remains crystalline with respect to the loss of the non-framework water molecules but removal of the framework water molecules results in a rapid loss of framework stability and crystallinity. The work demonstrates the potential to design the structure and void volume of a hybrid framework material through directed formation of the extended two-dimensional inorganic component and the packing of the organic component within the interlayer region.© 2012 The Royal Society of Chemistry.