Synthesis of Ordered Aluminophosphate and Galloaluminophosphate Mesoporous Materials with Anion-Exchange Properties Utilizing Polyoxometalate Cluster/Surfactant Salts as Precursors

Ordered non-lamellar mesoporous aluminophosphates and galloaluminophosphates have been synthesized by introducing phosphate linking groups to cluster/surfactants salts of pre-arranged AlO4Al12(OH)24(H2O)127+ (Al13) and GaO4Al12(OH)24(H2O)127+ (GaAl12) tridecamers. The Al13 and GaAl12 polyoxocations form a layered mesoscopic salt with the anionic surfactant sodium dodecylsulfate. Upon the reaction with a buffered hydrogenphosphate/dihydrogenphosphate solution the layers of clusters are transformed into a non-layered, nearly hexagonal mesoscopic phase. Removal of the surfactant from the alumino- and galloaluminophosphates by anion-exchange results in mesoporous materials with BET surface areas up to 630 and 455 m2/g, respectively. FT-IR, 27Al and 31P MAS NMR, as well as 27Al Æ 31P cross-polarization experiments indicate that the phosphate treatment results in the formation of new bonds between aluminate and phosphate species. A fraction of the clusters are transformed leading to an increase in the number of tetrahedral aluminate groups in the product. Multiple anion-exchange, e.g., with acetate, dichromate or napthol yellow S ions, is possible in these open mesoporous structures, which form a new class of inorganic anion-exchangers.