Manganese-modified hexagonal mesoporous aluminophosphate MnHMA: Synthesis and characterization

Manganese-modified hexagonal mesoporous aluminophosphate (MnHMA) was synthesized hydrothermally in a microwave oven in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The mesoporous structure was elucidated by HRTEM. Local environment of aluminum and phosphorus forming the mesoporous aluminophosphate framework was studied by MAS NMR. The local environment of manganese incorporated in HMA was investigated by X-ray absorption spectroscopy. XANES studies show that manganese in the as-synthesized and template-free MnHMA is present in the form of Mn2+ and Mn3+ ions in the ratio 40–60%. EXAFS analyses revealed four oxygens in the first coordination sphere of manganese in the as-synthesized and template-free MnHMA at the distances 2.142(5) Å and 2.15(1) Å, respectively. EPR and ESEEM measurements revealed that Mn2+ in both as-synthesized and template-free products was located within the mesoporous aluminophosphate framework.