Mixed-bonded open-framework aluminophosphates and related layered materials

The structural features, the synthesis and the role of templates in the synthesis for mixed-bonded open-framework aluminophosphates and related layered materials will be reviewed in this article. These aluminophosphate materials differ from the (4,2)-connected aluminophosphates and zeolites in that they contain TO5 and/or TO6 primary building units or terminal T-O bonds (T stands for Al or P). The extra ligands for the TO5 and TO6 units in the aluminophosphates with framework Al/P = 1 are either bridging OH groups or H2O molecules in most cases whereas the terminal T-O bonds are either P-OH or P=O species with P=O bonds being prevalent in layered aluminophosphates. Most of TO5 or TO6 containing aluminophosphates are prepared using a cyclic amine or a diamine as the structure directing agent (template), and the aluminophosphates with Al/P < 1 or the layered materials tend to form from an alcoholic medium. Both synthetic conditions and templates play a critical role in determining the composition and structural feature of these materials.