From octahedral open structures to octahedral tetrahedral open structures: Synthesis, characterization and catalysis of manganese oxides and manganese (oxo- and/or hydroxo-) phosphates

Date of Completion

January 2001


Chemistry, Inorganic




Novel preparation methods were employed to explore the richness of the synthetic chemistry of manganese oxide. Surfactant cations, tetradecyl-trimethyl-ammonium (TTA+), were directly intercalated into sodium birnessite to expand the microporous layered structure into a meso-structural one. Organization of the surfactant cations of the intercalated product is similar to that of the pure surfactant. Manjiroite was prepared as a single product for the first time. Very uniquely, this Na-OMS-2 has a meso and micro dual porosity. The morphology is comprised of multiple threads of tiny Na-OMS-2 crystals that form a knotted 3-dimensional network. ^ Synthetic strategies have been designed to introduce phosphate groups into the octahedral framework of manganese oxides. A few new materials with octahedral tetrahedral open structures have been synthesized. MPOS-3, Na 2Mn2O(PO4)2H2O has a rigid layered structure. MPOS-4, Na2Mn(HPO4)(PO4) is a chiral molecular sieve. MPOS-5, Na0.437MnO1.764(PO 4)0.236·xH2O is a mixed valent microporous material. ^ Various instrumentation methods were used to characterize the above materials. MPOS-3 demonstrated fair catalytic activity in the gas phase partial oxidation reaction of 2-propanol to acetone with carbon dioxide as the only by-product. The mixed valent manganese oxide and phosphate materials can be used as efficient catalysts in the partial oxidation of benzylic alcohols to aldehydes by air. ^