Joy Heising

New micro- and mesoporous materials based on VOPO4 chemistry

Abstract A brief review of porosity in zeolites, pillared layers and the new mesoporous materials serves as an introduction to the present study. A dark green-layered vanadyl phosphate of composition [(VO) 3 (PO 4 ) 3 (H 2 O) 3 ]·4H 2 O was prepared hydrothermally. It was found to intercalate close to 3 mols of amine per VOPO 4 unit. These amine-intercalated phases react with inorganic polymers in alcohol as the solvent under reflux to yield both micro- and mesoporous materials. These reactions exhibit features of both pillaring and template guided reactions. Materials with very narrow pore distributions are obtained by an, as yet, undetermined mechanism. Thermal treatment leads to larger pores with a still narrow pore size distribution. The goal is to prepare catalytically active porous materials with pore diameters in the 10–20 A range.

New families of supermicroporous metal oxides: the link between zeolites and mesoporous materials.

Sol-gel hydrolysis reactions in propanol of two or more metal acetates or alkoxides in n-alkylamines have been found to yield porous mixed oxides with the presence of pores largely in the 10-20 A region.

High real-space resolution structure of materials by high-energy x-ray diffraction

Results of high-energy synchrotrons radiation experiments are presented demonstrating the advantages of the atomic Pair Distribution Function technique in determining the structure of materials with high resolution.

Structure and thermoelectric properties of SrBiTe3; 12-fold superstructure caused by distortion of the two-dimensional Te-Nets

The ternary compound, SrBiTe 3 , was prepared by the molten flux method. It crystallizes in the orthorhombic space group Pmmn with a=4.665(2)A, b=4.517(2)A, c=16.129A, and Z=2. The compound is composed of a NaCl-type [Bi 2 Te 4 ] 2- layer and a flat square (Te 2 ) 2- net with equal Te-Te distances of 3.24A. The Sr 2+ ions are stabilized between the layers in monocapped square antiprismatic sites. X-ray and electron diffraction studies reveal a 12-fold superstructure due to subtle distortions within the Te net of the compound. The superstructure was refined in the monoclinic space group C2 with a=27.923(5)A, b=32.228(6)A, c=4.5069(9)A, β=90.000(3)°. The compound is a semiconductor with a band gap value of 0.14 eV. It melts incongruently at 613 °C.