Synthesis and real structure of RUB-11, a novel high-density silica zeolite based on magadiite layers

The discovery of new zeolite framework types plays an important role in producing new porous materials for applications such as adsorption, catalysis, separation, etc. RUB-11, a new all-silica zeolite with high density (2.11 g cm−3), was synthesised at 160 °C from reaction mixtures consisting of SiO2/ethylenediamine/H2O in a xenon atmosphere of 30 bar for a long reaction time (140 d). Physico-chemical characterisation using solid-state NMR spectroscopy, SEM, TG-DSC and ATR-FTIR spectroscopy confirmed that RUB-11 is a framework silicate. The atomic structure was solved by 3D electron diffraction using the fast-automated diffraction tomography method. The structure model of monoclinic symmetry with lattice parameters of a0 = 7.3929(5) Å, b0 = 7.3942(3) Å, c0 = 26.1786(13) Å and β = 98.372(7)° (space group: Pc) was refined against electron diffraction data (dynamical refinement) and powder diffraction data. An additional distance-least-squares refinement confirmed the feasibility of forming a stress-free silica framework of RUB-11 topology. The chemical composition of RUB-11 per unit cell is 30 SiO2. The framework silicate RUB-11 is structurally closely related to layer silicate magadiite and can be regarded as an interlayer expanded zeolite (IEZ) based on magadiite-type layers. Both materials contain topologically identical, dense layers, named [m with combining low line][a with combining low line][g with combining low line] layers. In the case of RUB-11, these layers are interconnected via additional silicon atoms leading to a complete framework with a 2-dimensional pore system consisting of intersecting 8-ring channels. The synthesis route leading to RUB-11 is in contrast to typical IEZs, which are obtained in a two-step process. According to the electron diffraction data and the XRD powder patterns, RUB-11 has a disordered structure. A detailed analysis revealed that two different types of disorder concerning the stacking of layer-like building units (consisting of [m with combining low line][a with combining low line][g with combining low line] layers plus interconnecting silicon atoms) contribute to the real structure of RUB-11. It is surprising that the channel-like pores of RUB-11 are completely empty when separated from the reaction mixture

Synthesis and Crystal Structures of Two Crystalline Silicic Acids: Hydrated H-Apophyllite, H₁₆Si₁₆O₄₀ • 8–10 H₂O and H-Carletonite, H₃₂Si₆₄O₁₄₄

Hydrated H-Apophyllite (HH-Apo) and H-carletonite (H-Car) were synthesized at 0 °C by leaching an apophyllite and a carletonite single crystal in a large surplus of 1.2 molar hydrochloric acid. The XRD powder patterns of HH-Apo and H-Car were indexed with space group symmetries of P4/ncc and I4/mcm and lattice parameters of a = 8.4872(2) Å, c = 16.8684(8) Å and a = 13.8972(3) Å, c = 20.4677(21) Å, respectively. The crystal structures were solved based on model building of the structures of the precursors and a physico-chemical characterization. Rietveld structure refinements confirmed the structure models. HH-Apo and H-Car are among the very few crystalline silicic acids whose structures have been determined and confirmed based on a structure refinement. The structure of HH-Apo contains thin silicate monolayers that can be regarded as constructed by rings of interconnected [SiO3OH] tetrahedra which form a puckered silicate layer. A sheet of water molecules is intercalated between the silicate layers. There are no direct hydrogen bonds between the silanol groups, but there are hydrogen bonds of different strengths between the terminal O atoms of the silicate layers and the intercalated water molecules. The 1H MAS NMR spectrum presents a strong signal at 4.9 ppm related to the aforementioned bonds and interactions between the water molecules, as well as a small signal at 22.5 ppm corresponding to an extremely strong hydrogen bond with d(O...O) ≈ 2.2 Å. The structure of H-Car is free of structural water and consists exclusively of microporous silicate double-layers with 4-connected [SiO4] and 3-connected [SiO3OH] tetrahedra in a ratio of 1:1 and a thickness of 9.2 Å. Neighboring layers are connected to each other by medium–strong hydrogen bonds with O...O distances of 2.56 Å. The structure of HH-Apo decays within several hours while H-Car is stable. A topotactic condensation reaction applied to H-Car forms an irregularly condensed silicate which still contains the layers in a distorted form as building blocks

The structure of RUB-1, (C8H16N)6[B6Si48O108], a boron containing levyne-type zeolite, occluding N-methyl-quinuclidinium in the cage-like pores

C48H96B6N6O108Si48, trigonal, R3‾m$R\overline{3}m$ (no. 166), a = 12.8892(1) Å, c = 22.3058(2) Å, V = 3209.23(4) Å3, Z = 1, density = 2.02(2) g·cm−3, R(F) = 0.038, Chi2 = 2.86, T = 293 K

Synthesis and real structure of RUB-11, a novel high-density silica zeolite based on magadiite layers

The discovery of new zeolite framework types plays an important role in producing new porous materials for applications such as adsorption, catalysis, separation, etc. RUB-11, a new all-silica zeolite with high density (2.11 g cm-3), was synthesised at 160 degrees C from reaction mixtures consisting of SiO2/ethylenediamine/H2O in a xenon atmosphere of 30 bar for a long reaction time (140 d). Physico-chemical characterisation using solid-state NMR spectroscopy, SEM, TG-DSC and ATR-FTIR spectroscopy confirmed that RUB-11 is a framework silicate. The atomic structure was solved by 3D electron diffraction using the fast-automated diffraction tomography method. The structure model of monoclinic symmetry with lattice parameters of a0 = 7.3929(5) angstrom, b0 = 7.3942(3) angstrom, c0 = 26.1786(13) angstrom and beta = 98.372(7)degrees (space group: Pc) was refined against electron diffraction data (dynamical refinement) and powder diffraction data. An additional distance-least-squares refinement confirmed the feasibility of forming a stress-free silica framework of RUB-11 topology. The chemical composition of RUB-11 per unit cell is 30 SiO2. The framework silicate RUB-11 is structurally closely related to layer silicate magadiite and can be regarded as an interlayer expanded zeolite (IEZ) based on magadiite-type layers. Both materials contain topologically identical, dense layers, named mag layers. In the case of RUB-11, these layers are interconnected via additional silicon atoms leading to a complete framework with a 2-dimensional pore system consisting of intersecting 8-ring channels. The synthesis route leading to RUB-11 is in contrast to typical IEZs, which are obtained in a two-step process. According to the electron diffraction data and the XRD powder patterns, RUB-11 has a disordered structure. A detailed analysis revealed that two different types of disorder concerning the stacking of layer-like building units (consisting of mag layers plus interconnecting silicon atoms) contribute to the real structure of RUB-11. It is surprising that the channel-like pores of RUB-11 are completely empty when separated from the reaction mixture.The discovery of new zeolite framework types plays an important role in producing new porous materials for applications such as adsorption, catalysis, separation, etc