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

Abstract

We report here the hydrothermal synthesis, crystal structure and properties of the hybrid inorganic–organic framework material Al₂[O₃PC₆H₄PO₃](H₂O)₂F₂·2H₂O which is the seventh member of the group 13 metal diphosphonate framework series of formula M^(III)₂[O₃PRPO₃](H₂O)₂F₂. The structure is formed from linear chains of corner-sharing AlO₄F₂ 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.