No abstract

A general synthetic method for the preparation of nanostructured materials with large surface area was developed by using nanoparticle building blocks. The preparation route involves the self-assembly of functionalized nanoparticles in a liquid-crystal phase. These nanoparticles are functionalized by using difunctional amino acid species to provide suitable interactions with the template. Optimum interactions for self-assembly of the nanoparticles in the liquid-crystal phase were achieved with one -NH2 group anchored to the nanoparticle surface per 25 A(2). To maximize the surface area of these materials, the wall thicknesses are adjusted so that they are composed of a monolayer of nanoparticles. To form such materials, numerous parameters have to be controlled such as the relative volume fraction of the nanoparticles and the template and size matching between the hydrophilic component of the copolymer and nanoparticles. The surface functionalization renders our synthetic route independent of the nanoparticles and allows us to prepare a variety of nanostructured composite materials that consist of a juxtaposition of different discrete oxide nanoparticles. Examples of such materials include CeO2, ZrO2, and CeO2-Al(OH)3 composites.

The framework gallium diphosphonates Ga2[O3PC2H4PO3](H2O)2F2·2H2O (1) (triclinic, P1̄, a = 5.0432(2) Å, b = 7.2468(3) Å, c = 8.3499(4) Å, α = 107.489(2)°, β = 92.444(2)°, γ = 109.338(2)°, Z = 1) and Ga2[O3PCH2(C6H4)CH2PO3](H2O)2F2 (2) (triclinic, P1̄, a = 4. 9673(1) Å, b = 7. 0898(2) Å, c = 10. 1220(3) Å, α = 92. 698(2)°, β = 93.153(2)°, γ = 109. 122(2)°, Z = 1) and the solid-solution series Ga2{[O3PCH2(C6H4)CH2PO3]1 - x (HPO3)2 x }(H2O)2F2 (0 ≤ x ≤ 0.146) x = 0.541 (3) and x = 0.144 Ga2{[O3PCH2(C6H4)CH2PO3]0.853(6)(HPO3)0.29(1)}(H2O)2F2 (4) (triclinic, P1̄, a = 4.959(2) Å, b = 7.078(2) Å, c = 10.024(3) Å, α = 92.404(5)°, β = 92.955(5)°, γ = 109.187(5)°, Z = 1) have been synthesized by solvothermal methods and their structures determined using X-ray diffraction data. All the materials contain linear chains of corner-sharing GaO4F2 octahedra that are linked by the diphosphonate groups to form framework structures. The channels of 1 are found to contain two water molecules per unit cell while those in 2 are too narrow to contain extraframework species. The apertures created in the phosphite-substituted derivatives of 2 (3 and 4) are shown, by crystallographic methods, to be considerably larger than those in 2 and, by thermogravimetric methods, to create more open structures. The synthetic conditions or form of the diphosphonate group are found to play a defining role in the adoption of this particular configuration of the inorganic component in the reported compounds and provide an additional strategy for the rational design of framework hybrid organic−inorganic solids.

We report here on the solvothermal synthesis and crystal structure of the hybrid organic-inorganic framework material Al(2)[O(3)PC(3)H(6)PO(3)](H(2)O)(2)F(2).H(2)O (orthorhombic, Pmmn, a = 12.0591(2) A, b = 19.1647(5) A, c = 4.91142(7) A, Z = 4), the second member of the Al(2)[O(3)PC(n)H(2n)PO(3)](H(2)O)(2)F(2).H(2)O series. The structure consists of corrugated chains of corner-sharing AlO(4)F(2) octahedra in which alternating AlO(4)F(2) octahedra contain two fluorine atoms in a trans or a cis configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the propylene groups to form a three-dimensional framework structure containing a one-dimensional channel system. The linkage of the corrugated inorganic Al-O-P layers within the structure results in the formation of two types of channel that differ in size, shape and composition. The smaller channel is unoccupied; the larger channel is more elongated and contains two extra-framework water molecules per unit cell. A computational investigation into the driving force that controls the stacking arrangement of the Al-O-P inorganic layers within this series of compounds reveals that the stacking is found to be controlled by thermodynamic factors, arising chiefly from the conformation of the organic linker molecule used to connect the inorganic sheets. It is found that the registration of the inorganic layers can be engineered by selecting an appropriate, simple organic spacer or linker alkyl chain, where an even number of carbon atoms in the alkyl chain directs formation of aligned, stacked, inorganic sheets (AAAAAA), and an odd number directs formation of unaligned, stacked sheets (ABABAB) and the formation of one or two channel types in the resultant structure, respectively. This combination of alkyl-chain linkers in conjunction with corrugated inorganic layers is an effective tool to rationally design the pore system of hybrid framework materials.

Members of the new solid solution aluminum phosphite/ ethylenediphosphonate series, Al2[(O3PC2H4PO3)1 - x (HPO3)2 x ](H2O)2F2·H2O (0 ≤ x ≤ 0.32), have been prepared and fully characterized. The full dehydration behavior of the parent material of this series, Al2[O3PC2H4PO3](H2O)2F2·H2O (x = 0) has been resolved. On heating the material to 230 °C the extraframework water is the primary species desorbed and the framework structure remains intact as determined from the crystal structure of the partially dehydrated material, Al2[O3PC2H4PO3](H2O)2F2·0.51(3)H2O. Above 150 °C, but more noticeably above 200 °C, framework water is lost, resulting in the formation of 4- and 5-coordinated Al centers. By 340 °C all the framework water and some fluorine is lost resulting in the collapse of the crystalline material. The phosphite substituted materials (0 < x ≤ 0.32) are shown, by diffraction and spectroscopic techniques, to be single-phase solid solutions. Rietveld refinement of the structure of the x = 0.19 member reveals that a random substitution of phosphite groups for diphosphonate species exists throughout the bulk of the material and that the remainder of the framework remains unaltered by incorporation of this moiety. The readsorption behavior of the materials (0 ≤ x ≤ 0.32) indicates that the temperature at which the extraframework water is first removed decreases as x increases and that the amount of water lost and degree of readsorption increase as x increases. These results indicate that the porosity of the materials can be controlled in a manner conducive to their rational design.