Synthesis and characterisation of mesoporous aluminophosphates containing boron

Mesostructured and mesoporous boroaluminophosphates (BAPO's) were synthesised using cationic templating in the presence of boric acid. The products were characterised by X-ray diffraction, ²⁷Al, ³¹P and ¹¹B solid-state NMR, thermal and elemental analysis, and nitrogen adsorption. Boron is incorporated into the structure, leading to a decrease in the degree of condensation of the inorganic component and to reduced thermal stability. Both tetrahedral and trigonal B is present in the structure of as-synthesised and calcined BAPO, but the B(4)-B(3) ratio is significantly reduced upon calcination. The kinetics of product formation were studied, and the likely mechanism of the synthesis is suggested, involving the formation of boroaluminophosphate oligomers which then react with the surfactant cations.