12-membered Ring Channels Research Articles

High-pressure behavior of synthetic mordenite-Na: an in situ single-crystal synchrotron X-ray diffraction study

Abstract The high-pressure behavior of a synthetic mordenite-Na (space group: Cmcm or Cmc21) was studied by in situ single-crystal synchrotron X-ray diffraction with a diamond anvil cell up to 9.22(7) GPa. A phase transition, likely displacive in character, occurred between 1.68(7) and 2.70(8) GPa, from a C-centered to a primitive space group: possibly Pbnm, Pbnn or Pbn21. Fitting of the experimental data with III-BM equations of state allowed to describe the elastic behavior of the high-pressure polymorph with a primitive lattice. A very high volume compressibility [K V0 = 25(2) GPa, β V0 = 1/K V0 = 0.040(3) GPa–1; K V ′ = (?K V /?P) T = 2.0(3)], coupled with a remarkable elastic anisotropy (β b >>β c >β a ), was found. Interestingly, the low-P and high-P polymorphs show the same anisotropic compressional scheme. A structure collapse was not observed up to 9.22(7) GPa, even though a strong decrease of the number of observed reflections at the highest pressures suggests an impending amorphization. The structure refinements performed at room-P, 0.98(2) and 1.68(7) GPa allowed to describe, at a first approximation, the mechanisms that govern the framework deformation in the low-P regime: the bulk compression is strongly accommodated by the increase of the ellipticity of the large 12-membered ring channels running along [001].

Molecular simulation of the adsorption of methane in Engelhard titanosilicate frameworks.

Molecular simulations were carried out to elucidate the influence of structural heterogeneity and of the presence of extra-framework cations and water molecules on the adsorption of methane in Engelhard titanosilicates, ETS-10 and ETS-4. The simulations employed three different modeling approaches, (i) with fixed cations and water at their single crystal positions, (ii) with fixed cations and water at their optimized positions, and (iii) with mobile extra-framework cations and water molecules. Simulations employing the final two approaches provided a more realistic description of adsorption in these materials, and showed that at least some cations and water molecules are displaced from the crystallographic positions obtained from single crystal data. Upon methane adsorption in the case of ETS-10, the cations move to the large rings, while in the case of ETS-4, the water molecules and cations migrate to more available space in the larger 12-membered ring channels for better accommodation of the methane molecules. For ETS-4, we also considered adsorption in all possible pure polymorph structures and then combined these to provide an estimate of adsorption in a real ETS-4 sample. By comparing simulated adsorption isotherms to experimental data, we were able to show that both the mobility of extra-framework species and the structural heterogeneity should be taken into account for realistic predictions of adsorption in titanosilicate materials.

Selective dealumination of mordenite for enhancing its stability in dimethyl ether carbonylation

Abstract Selective dealumination of mordenite by high-temperature steam treatment improved its stability in dimethyl ether carbonylation. Most of the framework Al species in the 12-membered ring channels of mordenite was removed while those in the 8-membered ring channels were retained. On the resulting mordenite catalyst, the formation rate of methyl acetate was only slightly decreased and maintained at 1.71 mol (mol H+)− 1 h− 1 at 15 h. Temperature-programmed oxidation analyses on the used sample evidenced that the deposition of hard coke was effectively suppressed in the selectively dealuminated catalyst because of the reduced number of acidic sites in the 12-membered ring channels.

On the high-pressure behavior of gobbinsite, the natural counterpart of the synthetic zeolite Na–P2

An in situ high-pressure single-crystal X-ray diffraction study of gobbinsite, the natural counterpart of the synthetic zeolite Na–P2, was carried out up to 4.3GPa. No evidence of amorphization was observed within pressure-range investigated. Using a non-penetrating P-medium, two changes of the elastic behavior occur: the first at 1.1–1.3GPa and the second at 2.7–3.2GPa. Birch-Murnaghan equations of state truncated to the second order were used to fit the experimental P–V data within the three P-ranges (i.e. 0.0001–1.1, 1.3–2.7 and 3.2–4.3GPa), giving the following isothermal bulk moduli (KV0): 46.3(9), 52(8) and 28(6) GPa, respectively. The unit-cell compression is significantly anisotropic. In response to the applied pressure, the 8-membered ring channel parallel to [100] undergoes a significant increase of ellipticity, whereas the channel parallel to [010] undergoes a shrinking towards a circular shape at P≥1.3GPa. A partial re-organization of the H2O sites occurs between 1.1 and 1.3GPa, and new framework deformational modes onset at P≥3.2GPa, coupled with a change in the coordination environment of the extraframework cations.

The crystal structure and characterization of 2-D and 3-D indium phosphates synthesized from a water/ethylene glycol mixed-solvent system

Three indium phosphates [In16(HPO4)28(H2O)12](NH4)8(H2O)12 (1), [In2(OH)(HPO4)2(PO4)](H2O)(C6H18N2) (2) and [In3(HPO4)6](C2N2H10)(H3O)(H2O)2 (3) were solvothermally synthesized from water/ethylene glycol (EG) mixed solvent systems by using 1,3-propyldiamine (1,3-PDA), 2-methyl-pentamethylenediamine (MPMD) and diethylenetriamine (DETA) as structure directing agents (SDAs), respectively. Compound 1 consists of anionic layers of [In7(HPO4)14(H2O)6]7−, which are connected by InO6 octahedra to form an anionic three-dimensional (3-D) open framework with intersecting 12-membered rings channels. The channels are filled with charge-balancing ammonium cations and guest water molecules. Compound 2 possesses a 2-D layered structure consisting of anionic layers of [In2(OH)(HPO4)2(PO4)]2– formed by InO6 octahedra and PO4 tetrahedra, in which the protonated MPMD and water molecules lie between the layers. Compound 3 is constructed from a [3.3.3] propellane-like building unit made of strict alternation of InO6 octahedra and PO4H tetradedra, forming a 3-D open framework with intersecting 8- and 12-membered ring channels. The protonated water and ethylenediamine derived from the decomposition of DETA during the synthesis are located within the channels. The three compounds were characterized by powder X-ray diffraction (PXRD), single crystal X-ray diffraction, Fourier-transformed infrared (FT-IR) spectra, thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectroscope (ICP-AES) and elemental analyses.

Synthesis and characterization of a new open-framework zinc phosphite (4,4′-(C5H4N)2(CH2)3)·[Zn3(HPO3)4

Employing 4,4′-trimethylenedipyridine as a template, a new two-dimensional zinc phosphite (4,4′-(C5H4N)2(CH2)3)· [Zn3(HPO3)4] has been prepared at room temperature and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, powder X-ray diffraction, and thermogravimetric analysis. The compound crystallizes in the monoclinic space group P21/c, with cell parameters, a = 9.3309(19) A, b = 14.798(3) A, c = 33.637(7) A, β = 91.11(3)°, V = 4643.8(16) nm3 and Z = 4. The connectivity of the ZnO4 tetrahedra and HPO3 pseudo pyramids results in infinite corner-sharing 4-membered ring chains as second building units which are further linked by Zn-O-P bonds to form a 2-D layer that with interesting 8-membered ring channels along the [100] direction. The diprotonated 4,4′-trimethylenedipyridine molecules sit in the middle of the layers along the [100] direction and interact with the framework via hydrogen bonds.

A novel inorganic and organic mixture cations templated indium phosphate: Synthesis and crystal structure

A novel mixture cations templated indium phosphates, Li(C 2N 2H 10)[In 2(HPO 4) 3(PO 4)], has been synthesized under mild hydrothermal conditions and characterized by elemental analysis and FT-IR spectrum. The crystal structure of title compound was determined by single crystal X-ray diffraction data. It belongs to monoclinic, space group P2/ n with unit cell dimension a = 9.4692(13) Å, b = 9.1622(12) Å, c = 9.7063(14) Å, β = 117.5620(10)°. Its structure is characterized as a three-dimensional open-framework with 8-membered ring channels along a axis, where the inorganic lithium cation and organic double-protonated ethylenediamine cation are located and interact with the framework both electrostatically and via hydrogen bonds of N–H⋯O.

New zinc diphosphonates with bright tunable luminescence and 12-member ring channels

A zinc diphosphonate, (H2G)0.5[Zn3(L)(HL)]·3H2O (G = 4-picolylamine, H4L = 1-hydroxyl-2-(3-pyridyl)ethylidene-1,1-diphosphonic acid) displays a 3D pillared open-framework with ellipsoid-like 12MR channels, bright tunable luminescence and thermally stable up to 250 °C under an air atmosphere.

Hydrothermal synthesis and characterization of a new organically templated three-dimensional open-framework gallium phosphate–phosphite (C 6N 2H 18) 2(C 6N 2H 17)Ga 15(OH) 8(PO 4) 2(HPO 4) 12(HPO 3) 6·2H 2O

Using H 3PO 3 as a phosphorus source and oxalic acid as a reducing agent, the first three-dimensional open-framework gallium phosphate–phosphite formula as (C 6N 2H 18) 2(C 6N 2H 17)Ga 15(OH) 8(PO 4) 2(HPO 4) 12(HPO 3) 6·2H 2O ( 1), has been hydrothermally synthesized in the presence of N,N,N′,N′-tetramethylenediamine (TMEDA) as a structure-directing agent. Compound 1 crystallizes in trigonal system with space group P − 3, a = b = 19.046(3) Å, c = 8.3306(17) Å, γ = 120°, V = 2617.1(7) Å 3, and Z = 1. Its 3-D network is based on alternated Ga-centered (GaO 4 tetrahedra, GaO 5 trigonal bipyramids, and GaO 6 octahedra) and P-centered (PO 4 3−, HPO 4 2−, and HPO 3 2−) units. Protonated organic amines and water molecules are located in the 12-membered ring channels.

Hydrothermal synthesis and structure of three novel open-framework lanthanide sulfate–oxalates

Three novel hybrid open-framework lanthanide sulfate-oxalates, {[NH(4)][Ln(H(2)O)(SO(4))(C(2)O(4))]}(n) [Ln = Y (1), La (II), Sm (III)] have been synthesized via hydrothermal reaction, and characterized by single crystal X-ray diffraction, powder X-ray diffraction, infrared spectrophotometry, thermal gravimetric analysis and fluorescence analysis. These three compounds were isostructural, and all crystallized into the monoclinic system with space group of P2(1)/n. In their structures, LnO(8) dodecahedra, SO(4) tetrahedral and C(2)O(4) groups are linked to give rise to a three-dimensional open-framework, which contains two kinds of 12-membered ring channel systems running along the a and b axis, respectively. (C) 2010 Elsevier B.V. All rights reserved.

Hydrothermal syntheses, characterizations of novel three-dimensional indium phosphite and indium phosphite–phosphate with intersecting 8-membered ring channels: [In 3(H 2PO 3) 3(HPO 3) 4]·( trans-C 6N 2H 16) and [In 6(HPO 3) 8(H 2PO 3) 5(H 2PO 4)]·(C 3N 2H 12) 2

Two new three-dimensional indium phosphite and indium phosphite–phosphate [In 3(H 2PO 3) 3(HPO 3) 4]·( trans-C 6N 2H 16) 1 and [In 6(HPO 3) 8(H 2PO 3) 5(H 2PO 4)]·(C 3N 2H 12) 2 2 have been synthesized under hydrothermal conditions using 1,2-diaminocyclohexane (1,2-DACH) and 1,3-diaminopropane (1,3-DAP) as structure directing agents, respectively and further characterized by powder X-ray diffraction, single crystal X-ray diffraction, IR spectroscopy, TGA, ICP-AES and elemental analyses. These two compounds have the similar 3D inorganic framework structures with intersecting 8-membered ring (8-MR) channels. In compound 1, the diprotonated trans-1,2-DACH cations occupy the 8-MR channels along the [0 0 1] direction even though a mix of trans- and cis-isomers of 1,2-DACH molecules are added in the reaction mixture. Moreover, the chirality of trans-1,2-DACH alternates along the channels. It is noted that compound 2 is the first indium phosphite–phosphate compound. Crystal data: compound 1, monoclinic, C2/ c (No. 15), a = 18.675(4) Å, b = 10.220(2) Å, c = 13.419(3) Å, β = 98.29(3)°, V = 2534.4(9) Å 3, and Z = 4. Compound 2, orthorhombic, Pna2 1 (No. 33), a = 26.7974(9) Å, b = 9.8459(3) Å, c = 18.5441(6) Å, V = 4892.8(3) Å 3, and Z = 4.

Crystal Plane- and Size-Dependent Protein Adsorption on Nanozeolite

In this study, nanozeolites LTL with different exposed crystal planes and sizes were synthesized as excellent model material to study the effects of the crystal plane and size of the nanozeolite on the protein adsorption behaviors. A larger protein adsorption amount is observed on the smaller nanocrystals due to their larger surface area. More importantly, it is found that the (001) crystal plane with a 12-membered ring channel array has a larger contribution for protein adsorption on zeolite LTL nanocrystals than the other two dimensions with a very small pore opening (1.5 Å). It is proposed that the difference of protein adsorption on various crystal planes could be attributed to abundant exposed pore openings on the top (bottom) surface and curved surface of the side surface in columned nanozeolites LTL. This fact shows that the nanoscaled topography is also an important factor determining protein adsorption on the surface of nanozeolites, and efforts in the future should be focused on the synthesis of nanozeolites LTL with abundant exposed (001) planes. This observation will provide a new view for bioapplication and design of crystalline nanomaterials.

Organic template-directed indium phosphite-oxalate hybrid material: Synthesis and characterization of a novel 3D |C6H14N2|[In2(HPO3)3(C2O4)] compound with intersecting channels

A novel anionic three-dimensional indium phosphite-oxalate hybrid material, formulated as |C6H14N2|[In2(HPO3)3(C2O4)] (1) was prepared under hydrothermal conditions by using 1,4-diazabicyclo[2.2.2]octane (dabco) as a structure directing agent (SDA). Single-crystal X-ray diffraction analysis reveals that compound 1 crystallizes in the orthorhombic system space group Pna21 (No. 33) having unit cell parameters a = 12.4143(13) Å, b = 7.7166(8) Å, c = 18.327(2) Å, V = 1755.6(3) Å3, and Z = 4 with R1 = 0.0282, wR2 = 0.0632. The novel 3D open framework is constructed from InO6 octahedra, HPO3 pseudo-tetrahedra and C2O4 units. The assembly of these building units generates intersecting 8- and 12-membered ring (MR) channels along two different directions. To the best of our knowledge, it is the first reported indium phosphite-oxalate hybrid material. Further characterization of compound 1 was performed using X-ray powder diffraction (XRD), infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP) and elemental analyses.

Mobility of acidic protons in zeolites: A neutron diffraction study of d-heulandite

Neutron Rietveld refinement of a natural heulandite (Si/Al = 3.1) in its deuterium form was performed in space group C2/ m. Two Brønsted acid sites were identified. One was on framework oxygen O1, occupied to 20% and headed toward the center of the 8-membered ring channel running parallel to [1 0 2]; the other was on O6, occupied to 30% and headed toward the 10-membered ring channel running parallel to the c-axis. Three other extraframework sites, located around a distance of 3 Å from the framework oxygens, were attributed to reabsorbed H 2O molecules. On the whole, about 3.2 Brønsted acid sites were located representing about 37% of the value expected on the basis of the aluminium content. This discrepancy is attributed to proton transfer from the Brønsted site to reabsorbed H 2O molecules, forming either a hydroxonium ion (H 3O +) or charged clusters such as (H 5O 2) + and (H 7O 3) +.

Synthesis, characterization of a new open-framework gallium phosphite containing 5,6-fold coordinate gallium atoms

A new open-framework gallium phosphite Ga 5(OH) 2(HPO 3) 8(C 4N 3H 16) · 2H 2O ( 1) is synthesized solvothermally using diethylenetriamine (DETA) as template from a mixed solvent system in which ethylene glycol (EG) was used as the co-solvent. The as-synthesized product is characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis (TGA), ICP-AES and elemental analyses. The three-dimensional open-framework of compound 1 is constructed from two novel secondary building units (SBUs), Ga 2O 7(OH)(HPO 3) three-membered ring (3R) and Ga(HPO 3) 6 tooth-wheel type unit. These two novel secondary building units are first found in gallium phosphate/phosphite, which lead to form the one-dimensional 8-membered ring channels along the a-axis. Moreover, it is noted that compound 1 is the first gallium phosphite containing 5-fold coordinate gallium atom.

Na5(NH4)Mn3[B9P6O33(OH)3]·1.5H2O

The overall hexa­gonal framework of the title compound, penta­sodium ammonium trimanganese(II) borophosphate sesquihydrate, consists of tube-like borophosphate anions, ∞ 1{[B3P2O11(OH)]4−}, made up of corner-sharing PO4 and BO4 tetra­hedra and BO2(OH) triangles, forming ten-membered ring windows. The tubes are inter­connected via distorted MnO6 octa­hedra, establishing a three-dimensional open-framework structure with two different types of ring-channels (12- and six-membered) that run along [001]. The 12-membered ring channels are occupied by NH4 + ions and water mol­ecules. The ten-membered ring windows in the walls of the tubes are occupied by Na+ ions. The remaining Na+ ions and the water mol­ecules, one of which is half-occupied, reside within the six-membered ring channels. The structural setup is consolidated by an O—H⋯O hydrogen bond between the OH group and an opposite O atom of the framework. Donor–acceptor distances ranging from 2.80 to 3.35 Å between the ammonium N atom, water O atoms and framework O atoms indicate further hydrogen-bonding inter­actions.

Synchrotron powder diffraction characterization of the zeolite-based (p-N,N-dimethylnitroaniline–mordenite) guest–host phase

The crystal structure of a new phase consisting of the inclusion of the hyperpolarizable molecule p-N,N-dimethylnitroaniline (dimethyl-para-nitroaniline or dmpNA) in the large-pore zeolite mordenite (MOR) has been determined from high-resolution synchrotron powder diffraction at 300 and 90 K. The unit-cell parameters and space group at 300 K are similar to those of as-synthesized mordenite. The crystallographic study indicates that the MOR straight channels are almost fully loaded with molecules that are disordered over eight symmetry-related sites. As expected, the molecules are located in the large 12-membered ring channel, at the intersection with the secondary eight-membered channel with which they might form hydrogen bonds. The elongation axes (and then the dipole moments) of the molecules are slightly tilted (28.57 degrees ) from [001]. The configuration found suggests an interaction of dmpNA with framework O atoms through its methyl groups.

Crystal structure of MCM-71 – a new zeolite in the mordenite group

Abstract The crystal structure of the aluminosilicate, MCM-71, was determined by a match of the powder X-ray diffraction pattern to one calculated from a theoretically predicted framework model. The unit cell contains 48 T-sites and 96 framework oxygens, where T = 41.1 Si, 6.9 Al. It crystallizes in space group Cmca, a = 7.4422(2), b = 18.5324(5), c = 19.1877(5) Å. The framework contains an elliptical 10-membered ring channel (4.3 × 6.5 Å) and an orthogonal undulating 8-membered ring channel (3.6 × 4.7 Å) to constitute a two-dimensional network of channels. Considering the aluminosilicate framework as a silicate, the crystal density is 1.77 g/cm3 and the T-site framework density is 17.8 T/1000 A3. The structure was refined against Debye-Scherrer and Bragg-Brentano powder synchrotron data by the Rietveld procedure. While non-framework oxygen atoms, consistent with water content, could be justified by TGA measurements, it was not possible to derive an accurate extra-framework model using synchrotron data from hydrated specimens. Refinement against powder data from an anhydrous specimen subsequently detected the presence of extra-framework aluminum, identified also by solid state NMR measurements.

Molecular mechanics studies of thionin blue in zeolite mordenite

The localization and arrangement of thionin blue (C 12H 10N 3S +) dye molecules in the zeolite mordenite framework is studied by molecular mechanics (MM) simulations. The computational results for dye molecule localization are compared to those from single crystal X-ray diffraction. Two low energy thionin orientations are observed. In both, the thionin molecules are inclined within the large 12-membered ring channels and indicate electrostatic interaction with the framework and with the extra-framework Na + ions. Molecule orientation and the determined S⋯O (3.12 and 3.13 Å), N⋯O (3.22 and 3.33 Å) and C⋯O (3.45 and 3.41 Å) distances from the dye molecule to the channel wall are in reasonable agreement with the values found by single crystal X-ray diffraction (S⋯O = 3.084 Å, N⋯O = 3.087 Å and C⋯O = 3.235 Å). Clustering of thionin molecules in the 12-membered ring channels is not observed. The calculated potential energies for these two low energy configurations are essentially the same (∼−2236 kJ/mol) The global minimum was confirmed by multiple simulation runs, using different starting orientations of the thionin molecules in the mordenite framework. Quench simulations were also performed to understand the energetics of diffusion of thionin molecules in mordenite. The calculated activation energy of diffusion, ∼12–15 kJ, is comparable to values reported in literature for molecular diffusion in zeolites.

Mix-Solvothermal Syntheses, Characterization, and Properties of New Zinc Diphosphonates with Zn−O−P Chains, Layers, and 3D Frameworks

Eight new zinc diphosphonates, [NaZn(O3P(CH2)2PO3H)] (1), [K2Zn2(HO3P(CH2)2PO3H)(O3P(CH2)2PO3)] (2), [(NH4)(H3N(CH2)2NH3)0.5Zn3(O3P(CH2)2PO3)2] (3), [(NH4)2Zn3(O3P(CH2)3PO3)2] (4), [(H3N(CH2)4NH3)0.5Zn(O3P(CH2)3PO3H)] (5), [KZn(O3P(CH2)4PO3H)] (6), [KZn(HO3P(CH2)4PO3H)(Cl)] (7), and [NH4Zn(O3P(CH2)4PO3H)] (8), have been successfully synthesized under mixed solvothermal conditions and characterized by X-ray single-crystal diffraction together with elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. In 1 and 2, 1,2-ethylenediphosphonate groups combine cations (Na+, K+) and Zn−O−P layers into 3D frameworks, while in 3 and 4, ethylene and propylene groups are enclosed in novel 3D Zn−O−P frameworks, respectively, which possess 8-membered ring (8MR) and 12MR channels. In 5−8, Zn−O−P infinite chains are pillared by 1,3-propylene- and 1,4-butylenediphosphonate groups into hybrid layers. It is interesting that in 7 K−Cl lamellae link the Zn−O−P hybrid layer to form a 3D sandwichlike framework. If 1 is synthesized with commercial fluorescent whitener (disodium 4,4‘-bis(2-sulfonatostyryl)biphenyl) in the initial reaction mixture, it exhibits bright purple-blue luminescence with a short lifetime. Photoluminescent properties of 4 and 8 are also discussed.