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

Ordered nonlamellar mesoporous aluminophosphates and galloaluminophosphates have been synthesized by introducing phosphate linking groups to cluster/surfactants salts of prearranged AlO 4 Al 12 (OH) 24 (H 2 O) 12 7+ (Al 13 ) and GaO 4 Al 12 (OH) 24 (H 2 O) 12 7+ (GaAl 12 ) tridecamers. The Al 13 and GaAl 12 polyoxocations form a layered mesoscopic salt with the anionic surfactant sodium dodecylsulfate. Upon the reaction with a buffered hydrogen phosphate/dihydrogen phosphate solution the layers of clusters are transformed into a nonlayered, 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 m 2 /g, respectively. FT-IR and 27 Al and 31 P MAS−NMR as well as 27 Al → 31 P 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 naphthol yellow S ions, is possible in these open mesoporous structures, which form a new class of inorganic anion-exchangers.