Interlayer Voids Research Articles

Using NMR in Structural Studies of Aluminum Hydroxide Intercalation Compounds with Lithium Salts

The effect of the anion charge on the structure of [LiAl2(OH)6]nX (X = Cl-, Br-, I-, SO42-, C6H8O42-) intercalation compounds and the water effect on the structure of [LiAl2(OH)6]Cl·nH2O have been studied using 1H, 7Li, and 27Al NMR. A change in the charge on the anion leads to significant changes in the asymmetry parameter for the lithium and aluminum nuclei with relatively small changes in the quadrupolar coupling constant and the broadening factor. The structure of the intermediate [LiAl2(OH)6]Cl·0.5H2O hydrate can be represented as a derivative of the structure of the anhydrous [LiAl2(OH)6]Cl intercalate with a slightly increased layer thickness and a minor orthorhombic distortion of the hexagonal cell; the water molecules partially fill the interlayer voids and participate in the diffusion process. Further hydration of the intercalate (x ≥ 1) leads to a minor (0.2A) increase in the layer thickness and is accompanied by disordering of chloride ions and water molecules in the interlayer space.

Synthesis and Characterization of an Organically Templated Lamellar Vanadium–Gallium Phosphate, [NH3(CH2)2NH3]4[Ga4–xVx(HPO4)5(PO4)3H(OH)2](x=1.65)

A new two-dimensional vanadium–gallium phosphate (VGaPO), [NH3(CH2)2NH3]4[Ga4–xVx(HPO4)5(PO4)3H(OH)2](x=1.65), has been synthesized under solvothermal conditions at 433 K in the presence of ethylenediamine and the structure determined using room-temperature single-crystal X-ray diffraction data (Mr=1296.22, triclinic, space group P–1; a=9.991(1), b=12.367(1), and c=15.082(1) Å; α=90.751(6), β=91.720(7), and γ=91.449(8)°; V=1861.8.4 Å3; Z=2; R=3.93% and Rw=4.77% for 5985 observed data (I>3(σ(I))). The inorganic layers consist of PO4 tetrahedra and M4O20 (M=V, Ga) tetramers assembled from edge- and corner-sharing MO6 octahedra. The structure contains various types of hydrogen bonding interactions: short symmetrical and asymmetrical hydrogen bonds within the layers, strong interlamellar hydrogen bonds holding the layers together, and amine-framework interactions holding the ethylenediammonium cations in place in the interlayer voids.

A zinc phosphate with laminar structure: (ZnPO 4) 4(H 2PO 4) 2(C 4N 2H 14) 2

A zinc phosphate compound with composition (ZnPO 4) 4(H 2PO 4) 2(C 4N 2H 14) 2 was synthesized by the hydrothermal reaction of zinc oxide and phosphoric acid in the presence of 1,4-diaminebutane. The crystal structure was solved from powder data and exhibits triclinic symmetry with a=8.6590(3) Å, b=10.3467(3) Å, c=8.3910(3) Å, α=102.180(2)°, β=93.676(2)° and γ=88.203(2)°. The new organo-zincophosphate has sheets built from saw-type four member ring ladders, where ZnO 4 and PO 4 tetrahedrons alternate. Additional phosphate groups project into the interlayer voids where the protonated amine resides.

Effects of Exchanged Cation and Layer Charge on the Sorption of Water and Egme Vapors on Montmorillonite Clays

AbstractThe effects of exchanged cation and layer charge on the sorption of water and ethylene glycol monoethyl ether (EGME) vapors on montmorillonite have been studied on SAz-1 and SWy-1 source clays, each exchanged respectively with Ca, Na, K, Cs and tetramethylammonium (TMA) cations. The corresponding lattice expansions were also determined, and the corresponding N2 adsorption data were provided for comparison. For clays exchanged with cations of low hydrating powers (such as K, Cs and TMA), water shows a notably lower uptake than does N2 at low relative pressures (P/P0). By contrast, EGME shows higher uptakes than N2 on all exchanged clays at all P/P0. The anomaly for water is attributed to its relatively low attraction for siloxane surfaces of montmorillonite because of its high cohesive energy density. In addition to solvating cations and expanding interlayers, water and EGME vapors condense into small clay pores and interlayer voids created by interlayer expansion. The initial (dry) interlayer separation varies more significantly with cation type than with layer charge; the water-saturated interlayer separation varies more with cation type than the EGME-saturated interlayer separation. Because of the differences in surface adsorption and interlayer expansion for water and EGME, no general correspondence is found between the isotherms of water and EGME on exchanged clays, nor is a simple relation observed between the overall uptake of either vapor and the cation solvating power. The excess interlayer capacities of water and of EGME that result from lattice expansion of the exchanged clays are estimated by correcting for amounts of vapor adsorption on planar clay surfaces and of vapor condensation into intrinsic clay pores. The resulting data follow more closely the relative solvating powers of the exchanged cations.

Sol-gel synthesis of birnessite from KMnO4 and simple sugars

Birnessite is a naturally occurring manganese oxide that has been identified as a major constituent of deep sea manganese nodules. The mineral consists of layers of edge- and corner-linked MnO{sub 6} octahedra with water molecules and alkali-metal cations in the interlayer voids. A generalized elemental composition of birnessite is A{sub x}MnO{sub 2{plus_minus}y}{sm_bullet}zH{sub 2}O, in which A represents an alkali-metal cation. Natural and synthetic birnessites with an octahedral layered (OL) structure have attracted significant interest because of their potential as heterogeneous catalysts and materials for secondary batteries. Birnessites are also precursors for tunnel structure manganese oxides such as cryptomelane and todorokite. Sol-gel processing of birnessites potentially offers numerous advantages over traditional methods of synthesis such as high-purity, particle-size homogeneity, and film-casting capability. However, very few sol-gel routes have been developed for materials with near-MnO{sub 2} stoichiometry such as birnessite. Early reports of manganese oxide gels described {open_quotes}MnO{sub 2} jellies{close_quotes} formed from reactions of KMnO{sub 4} with simple sugars. However, until now these systems remained poorly characterized. The authors have reinvestigated these manganese oxide gels and in the process discovered a new sol-gel method of preparing birnessite with interlayer potassium cations, K-OL-1. 26 refs., 3 figs.