On the crystallisation and nature of the microporous boron-aluminium oxo chloride BAC(10)

A novel microporous boron-aluminium oxo chloride [BAC(10)] has been synthesized hydrothermally. The crystallisation of the material was studied by X-ray diffraction (XRD), inductively coupled plasma analysis (ICP), IR spectroscopy and magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Its basic building units are triangular BO₃, tetrahedral BO₄ and octahedral AlO₆. As BAC(10) crystallises, some of the BO₃ groups are transformed into BO₄ species in the solid. Adsorption measurements reveal that BAC(10) has a microporous structure, whereas the fact that the CP ions in BAC(10) can be partially exchanged by Br ions suggests that this compound possesses a cationic framework. Thermal decomposition studies indicate that BAC(10) is stable up to 300°C, and at temperatures above 325°C the crystal structure of BAC(10) collapses with the evolution of HCl and H₂O from the sample.