Extra-framework Water Molecules Research Articles

In-situ dehydration study of the Sr-, Cd- and Pb-exchanged natrolite

The removal of Sr, Cd, and Pb from nuclear and industrial waste is important as these are harmful to living organisms and the environment. Immobilization of these ions in a zeolite framework is a simple and suitable method. However, zeolites are easily dehydrated at high temperatures. Therefore, the environmental changes around these adsorbed cations and water molecules in the zeolite framework must be explored for effective immobilization and waste removal. In this study, we investigated the structural changes in fully Sr-, Cd-, and Pb-exchanged natrolites (NAT) from room temperature to 350 °C using in situ synchrotron X-ray powder diffraction and Rietveld analysis. In the thermogravimetric analysis, Sr-NAT showed a gradual weight loss up to 210 °C, whereas Cd- and Pb-NAT showed a two-step weight loss in the ranges 90–280 °C and 100–180 °C, respectively. Sr-, Pb-, and Cd-NAT exhibited low thermal expansions with the thermal expansion coefficients of −3(1) × 10−6, −1.0(7) × 10−6, and 1(2) × 10−6 K−1, respectively, at the initial stage of increasing the temperature. During the dehydration process, the coefficients of Sr- and Cd-NAT were −2.7(7) × 10−4 K−1 up to 300 °C with a 2.9% volume contraction and −5.3 × 10−4 K−1 up to 150 °C with 2.7% volume contraction, respectively. At high temperatures, structurally, the Sr2+ and Cd2+ cations had six- and seven-coordinated bonding with framework oxygens and extra-framework species, whereas Pb2+ cations had three- and five-coordinated bonding. In contrast, the extra-framework water molecules in Sr-NAT had three to five bonds, Cd-NAT had five, and Pb-NAT had six. The chain rotation angle of the secondary building units (T5O10) increased in all cases, indicating that the channel shape becomes more elliptical during dehydration. Sr- and Pb-NAT were amorphized at 350 °C and 150 °C, whereas Cd-NAT remained intact. We concluded that Sr- and Pb-NAT were not thermally stable owing to the order-disorder transition of Sr2+ and high-disorder distribution of Pb2+, respectively. Our findings provide a fundamental understanding of the structural changes and mechanism of thermal stability in natrolites containing hazardous elements.

Detailed investigations of phase transitions and magnetic structure in Fe(iii), Mn(ii), Co(ii) and Ni(ii) 3,4,5-trihydroxybenzoate (gallate) dihydrates by neutron and X-ray diffraction

The effect of cation valency on the complex structures of divalent and trivalent transition metal gallates has been examined using a combination of neutron and synchrotron X-ray powder diffraction, single-crystal X-ray diffraction and XANES spectroscopy. In the divalent frameworks, M(C(7)H(4)O(5))·2H(2)O (M = Mn, Co and Ni), it was found that charge balance was achieved via the presence of protons on the meta-hydroxyl groups. It was also established that these compounds undergo a discontinuous phase transition at lower temperatures, which is driven by the position of the extra-framework water molecules in these materials. By contrast, in the trivalent Fe gallate, Fe(C(7)H(3)O(5))·2H(2)O, it was found that the stronger bonding between the meta-hydroxy oxygen and the cations leads to a weakening of the bond between this oxygen and its proton. This is turn is thought to lead to stronger hydrogen bonding with the extra-framework water. The lattice water is disordered in the Fe(III) case, which prevents the phase transition found in the M(II) gallates. Refinement against the neutron diffraction patterns also revealed that the relatively mild microwave synthesis of gallate frameworks in D(2)O led to an extensive deuteration of the ortho-hydrogen sites on the aromatic ring, which may suggest a more versatile method of deuterating aromatic organics. The antiferromagnetic structure of Co gallate has also been determined.

On the crystal structure and crystal chemistry of pollucite, (Cs,Na)16Al16Si32O96{middle dot}nH2O: A natural microporous material of interest in nuclear technology

The crystal structure and crystal chemistry of two natural pollucite samples, from Buckfield, Oxford County, Maine (sample M3), and from Kanzit Mawaie, Laghman, Nooristan, Afghanistan (sample N5), have been investigated by means of wavelength-dispersive X-ray microanalysis, thermogravimetric analysis, single-crystal X-ray and neutron diffraction, and single-crystal Fourier-transform infrared spectroscopy. The X-ray and neutron diffraction patterns of the two pollucite crystals show a metrically cubic unit cell [with a M3 = 13.6914(6) A and a N5 = 13.6808(6) A by neutron diffraction data; the deviation from isometry is l i ), where l i is the unrestrained unit-cell length] and the reflection conditions are consistent with the space group Ia 3 d . Anisotropic neutron structural refinements gave final agreement indices: R 1 = 0.0543 for 32 refined parameters and 372 unique reflections with F o > 4σ( F o ) for M3 and R 1 = 0.0693 for 31 refined parameters and 331 unique reflections with F o > 4σ( F o ) for N5. The structure refinements show a disordered Si/Al-distribution in the tetrahedral framework. The analysis of the difference-Fourier maps of the nuclear density confirms the presence of extra-framework water molecules with oxygen sharing the Cs site (at 1/8, 1/8, 1/8, Wyckoff-16 b position). However, the minima, ascribable to the proton sites, are very weak in density. Two possible proton positions, leading to a reasonable H 2 O configuration, are given, and the possible hydrogen bonding is described. Sodium is located at 1/4, 1/8, 0 (Wyckoff-24 c position). The main IR absorption bands in the regions typical of H 2 O are assigned, and the presence of hydroxyls in the studied samples is ruled out. Neutron diffraction and FTIR data agree with the presence of very weak hydrogen bonds in the structure. The detailed description of the crystal structure and crystal chemistry of pollucite (e.g., Si/Al-distribution, configuration of the extra-framework content, possible hydrogen bonding scheme) reported in this study is the key to understand the high thermo-elastic stability of pollucite, the immobility of Cs at non-ambient conditions, and the extremely low leaching rate of Cs, which make this open-framework silicate a promising material with potential use for fixation and deposition of Cs radioisotopes.

Fluorite and Mixed‐Metal Kagome‐Related Topologies in Metal–Organic Framework Compounds: Synthesis, Structure, and Properties

Two new three-dimensional metal-organic frameworks (MOFs) [Mn(2)(mu(3)-OH)(H(2)O)(2)(BTC)] x 2 H(2)O, I, and [NaMn(BTC)], II (BTC = 1,2,4-benzenetricarboxylate = trimellitate) were synthesized and their structures determined by single-crystal X-ray diffraction (XRD). In I, the Mn(4) cluster, [Mn(4)(mu(3)-OH)(2)(H(2)O)(4)O(12)], is connected with eight trimellitate anions and each trimellitate anion connects to four different Mn(4) clusters, resulting in a fluorite-like structure. In II, the Mn(2)O(8) dimer is connected with two Na(+) ions through carboxylate oxygen to form mixed-metal distorted Kagome-related two-dimensional -M-O-M- layers, which are pillared by the trimellitate anions forming the three-dimensional structure. The extra-framework water molecules in I are reversibly adsorbed and are also corroborated by powder XRD studies. The formation of octameric water clusters involving free and coordinated water molecules appears to be new. Interesting magnetic behavior has been observed for both compounds. Electron spin resonance (ESR) studies indicate a broadening of the signal below the ordering temperature and appear to support the findings of the magnetic studies.

Crystal chemistry of Rb-, Sr-, Ba-, Ca- and Pb-exchanged forms of natural hilairite

Cation-exchange properties of natural hilairite, Na 2 {ZrSi 3 O 9 }· 3H 2 O, in aqueous salt solutions at 150 °C and the crystal structures of its Rb-, Ca-, Sr-, Ba- and Pb-exchanged forms have been studied on single crystals. All studied samples retain the mixed framework of “parent” hilairite consisting of helical chains [Si 3 O 9 ] ∞ linked by isolated [ZrO 6 ] octahedra. The main differences between the crystal structures of these cation-exchanged forms of hilairite and other representatives of the hilairite group are connected with the number and positions of extra-framework cations and water molecules, framework distortion, unit-cell dimensions and space-group symmetry. The single-crystal structure refinements (X-ray diffraction data) gave the following structural formulas for the studied samples: Rb 1.80 Na 0.20 Zr[Si 3 O 9 ]·0.4H 2 O for Rb-exchanged hilairite ( R 3, a = 10.477(1), c = 15.377(2) A, R 1( F ) = 3.35% for 2771 reflections with F o > 4σ( F o )), Ba 0.96 H 0.08 Zr[Si 3 O 9 ]·3H 2 O ( R 3, a = 20.976(3), c = 7.857(2) A, R 1( F ) = 4.96% for 4921 reflections with F o > 4σ( F o )) and SrZr[Si 3 O 9 ]·1.5H 2 O ( R 3, a = 20.964(3), c = 7.836(2) A, R 1( F ) = 10.23% for 3598 reflections with F o > 4σ( F o )) for Ba- and Sr-exchanged hilairites, respectively, and Ca 0.83 H 0.34 Zr[Si 3 O 9 ]·3H 2 O ( R 3, a = 10.456(1), c = 7.995(2) A, R 1( F ) = 2.63% for 1477 reflections with F o > 4σ( F o )) and Pb 0.82 Na 0.18 H 0.18 Zr[Si 3 O 9 ]·2.9H 2 O ( R 3, a = 10.477(1), c = 7.994(2) A, R 1( F ) = 2.21% for 1165 reflections with F o > 4σ( F o )) for Ca- and Pb-exchanged hilairites, respectively. All samples were twinned by merohedry and, except the Ca-exchanged sample, also racemically. The results of this study strongly indicate that natural cation-exchange processes can affect hilairite-group minerals under late-hydrothermal conditions.

Reversible Water Intercalation Accompanied by Coordination and Color Changes in a Layered Metal−Organic Framework

A new two-dimensional 3d-4f mixed-metal mixed dicarboxylate (homocyclic and heterocyclic) of the formula [Gd(2)(H(2)O)(2)Ni(H(2)O)(2)(1,2-bdc)(2)(2,5-pydc)(2)].8H(2)O (1; 1,2-H(2)bdc = 1,2-benzenedicarboxylic acid and 2,5-H(2)pydc = 2,5-pyridinedicarboxylic acid) has been prepared by employing the hydrothermal method. The structure has infinite one-dimensional -Gd-O-Gd- chains formed by the edge-shared GdO(9) polyhedral units, resulting exclusively from the connectivity between the Gd(3+) ions and the 1,2-bdc units. The chains are connected by the [Ni(H(2)O)(2)(2,5-pydc)(2)](2-) metalloligand, forming the two-dimensional layer arrangements. The stacking of the layers creates hydrophilic and hydrophobic spaces in the interlamellar region. A one-dimensional water ladder structure, formed by the extraframework water molecules, occupies the hydrophilic region while the benzene ring of 1,2-bdc occupies the hydrophobic region. To the best of our knowledge, the present compound represents the first example of a 3d-4f mixed-metal carboxylate in which two different aromatic dicarboxylate anions act as the linkers. The stabilization energies of the water clusters have been evaluated using density functional theory calculations. The water molecules in 1 are fully reversible accompanied by a change in color (greenish blue to brown) and coordination around Ni(2+) ions (octahedral to distorted tetrahedral).

Hydration/Dehydration and Cation Migration Processes at High Temperature in Zeolite Chabazite

High temperature structural behavior of a natural chabazite of composition (Ca1.1Na0.4K0.7)[Si8.6Al3.4O24]·14.4H2O has been characterized by means of in situ HT single-crystal X-ray diffraction (SC-XRD) and thermogravimetric analysis. Lattice dimensions have been measured in the 25−700 °C range and crystal structure refined from XRD data collected at T = 25, 100, 125, 175, 250, 300, 425, and 600 °C. Variations of unit-cell parameters as a function of temperature reveal two discontinuities at 100 and 200 °C, to which no symmetry changes are associated, and an overall volume reduction of 2.8%. Between 200 and 250 °C, a steep contraction of cell volume is associated with a significant broadening of diffraction profiles, which turn sharp and narrow at higher temperatures. As the dehydration process proceeds with increasing T, cationic sites partly coordinated by extraframework water molecules become unstable and cations migrate toward new positions. Cations occupying the C2, C3, and C4 sites at room temperatu...

New insights into the crystal chemistry of epididymite and eudidymite from Malosa, Malawi: A single-crystal neutron diffraction study

The crystal chemistry of two dimorphic hydrated sodium beryllium silicates, epididymite [a = 12.7334(4), b = 13.6298(5), c = 7.3467(3) Å, V = 1275.04 Å 3 , space group Pnma)] and eudidymite [a = 12.6188(10), b = 7.3781(5), c = 13.9940(9) Å, β = 103.762(5)°, V = 1265.47 Å 3 , space group C2/c] from Malosa, Malawi, has been reinvestigated by means of energy dispersive X-ray spectroscopy, thermo-gravimetric analysis, inductively coupled plasma-optical emission spectroscopy and single-crystal neutron diffraction. Two anisotropic structure refinements have been performed with final agreement index R1 = 0.0317 for 137 refined parameters and 2261 unique reflections with F o > 4σ(F o ) for epididymite, and R1 = 0.0478 for 136 refined parameters and 1732 unique reflections with F o > 4σ(F o ) for eudidymite. The analysis of the difference-Fourier maps of the nuclear density of the two dimorphs confirms the presence of extra-framework water molecules in both, and not hydroxyl groups as wrongly reported in previous studies and in several crystal-structure databases. The correct chemical formula of edipidymite and eudidymite is Na 2 Be 2 Si 6 O 15 ·H 2 O (Z = 4). The configuration of the water molecules and the hydrogen bonds are fully described for both the dimorphs. The chemical analyses show that a small, but significant, amount of Al and Fe (most likely substituting for Si in the tetrahedral sites) and K (substituting for Na as an extra-framework cation) occurs in both dimorphs

Characterisation and properties of the n = 3 and n = 4 members of the Al 2[O 3PC nH 2 nPO 3](H 2O) 2F 2 framework aluminium alkylenediphosphonate series

A combination of techniques has been used to fully determine the structure and properties of Al 2[O 3PC 4H 8PO 3](H 2O) 2F 2·2H 2O (monoclinic, P2 1/ m, a = 4.96926(6) Å, b = 12.0013(1) Å, c = 10.7440(2) Å, β = 94.058(1)°, Z = 2, R p = 0.0732, R wp = 0.0939), the n = 4 member of the framework aluminium alkylenediphosphonate Al 2[O 3PC n H 2 n PO 3](H 2O) 2F 2 series. The combination of thermogravimetric and thermodiffraction data and the structure determination of the partially dehydrated structure, Al 2[O 3PC 4H 8PO 3](H 2O) 2F 2·0.17(1)H 2O (monoclinic, P2 1/ m, a = 4.9392(3) Å, b = 12.1867(4) Å, c = 10.7830(5) Å, β = 94.767(3)°, Z = 2, R p = 0.0839, R wp = 0.1121), indicate that the framework structure is stable to, and remains unchanged, with respect to the loss of the extra-framework water molecules but not the framework water molecules. This behaviour is in stark contrast to the n = 3 member of the Al 2[O 3PC n H 2 n PO 3](H 2O) 2F 2 series, Al 2[O 3PC 3H 6PO 3](H 2O) 2F 2·H 2O, for which the combination of thermogravimetric and thermodiffraction data indicates that the framework structure contracts during the loss of the extra-framework water molecules before collapsing after loss of the framework water molecules. The formation of the n = 4 member of the series indicates that the design of the alkyl chain can be used to successfully control aspects of the pore volume within this family of materials and comparison of the dehydration behaviour of the n = 3 and n = 4 members of the series indicates that related materials containing channels housing the same number of water molecules exhibit different dehydration behaviour depending on the stacking of the constituent inorganic layers within the material.

Synthesis and characteristic properties of Rb-mordenite

Rb-mordenite, namely RMA-1, with a Si/Al ratio of 5.3–8.3 in a pure phase was hydrothermally synthesized for the first time from Rb-aluminosilicate gel without using any organic structure-directing agent under stirring condition. The crystal structure was analyzed by the Rietveld refinement of the XRD data, and the sites of extra framework Rb ions and water molecules were determined. The adsorption properties of water and benzene on the mordenites with different Si/Al ratios were evaluated. The adsorption capacities of water and benzene on Rb-mordenites were lower than those of Na-mordenites because of larger ionic diameter of Rb.

A New Series of Three-Dimensional Metal−Organic Framework, [M2(H2O)][C5N1H3(COO)2]3·2H2O, M = La, Pr, and Nd: Synthesis, Structure, and Properties

A new series of lanthanide pyridine dicarboxylates of the general formula, [M2(H2O)][C5N1H3(COO)2]3.2H2O, M = La (1), Pr (2), and Nd (3), has been prepared by the reaction of trivalent lanthanide salts and pyridine dicarboxylic acids employing a mild condition hydrothermal reaction. The structures are built up from MO8N and MO7N2 (M = lanthanide) polyhedra connected to the dicarboxylate anions forming the three-dimensional structure with one-dimensional channels. A striking feature of this structure is the presence of an unusual Z-shaped tetramer of the formula M4O24N6. Extraframework water molecules, located within the open channels, are reversibly adsorbed. Detailed in situ and ex situ investigations using FTIR and PXRD studies clearly show that the removal of the water molecules is reversible and accompanied by changes in the size of the channel. Partial substitution at the La sites by Eu gives rise to characteristic red-pink luminescence, indicating a ligand-sensitized metal-centered emission.

Synthesis and Characterization of a Novel Germanate Material Containing 16-Ring Channels and Templated by a Simple Primary Amine

The new framework germanate (H3NC3H7)5(H3O)[Ge18O36(OH)6]·3H2O (tetragonal, I4cm, a = 24.9728(6) Å, c = 9.8957(2) Å, Z = 4) has been synthesized by solvothermal methods and the crystal structure determined using single-crystal X-ray diffraction data. The framework of this novel material contains a three-dimensional intersecting channel system, the two largest channels of which are encompassed by large circular 16-rings and elliptical 14-rings, respectively. The material is synthesized in the presence of the relatively small structure-directing agent isopropylamine. (H3NC3H7)5(H3O)[Ge18O36(OH)6]·3H2O is only the second material to be constructed from the secondary building unit [Ge9(O,OH)25] cluster, and the frameworks of these two materials are shown to differ only by the number of chains of [Ge9(O,OH)25] clusters that are used to construct the respective frameworks. Thermal stability studies indicate that the framework of the material is stable with respect to loss of the extraframework water molecules but is unstable with respect to the removal of the extraframework charge-compensating cations.

Synthesis and structure of the n = 4 member of the framework aluminium alkylenediphosphonate series Al2[O3PC n H2n PO3](H2O)2F2

We report here the solvothermal synthesis and crystal structure of the hybrid inorganic-organic framework material Al2[O3PC4H8PO3](H2O)2F2⋅2H2O (monoclinic, 1P21/m, a = 4.961(2) A, b = 11.930(5) A, c = 10.727(5) A, β = 93.972(6)∘, Z = 2, R(F, F2 > 2σ) = 0.094, Rw(F2, all data) = 0.262), the third member of the Al2[O3PCnH2nPO3](H2O)2F2 framework series. The structure is formed from corrugated chains of corner-sharing AlO4F2 octahedra in which alternating AlO4F2 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 butyl groups to form a three-dimensional framework structure containing a one-dimensional channel system consisting of one type of channel only. The channels contain four extra-framework water molecules per unit cell. The formation of this member of the series shows that the form of the alkyl chain can successfully define the number of channel types and the channel length in this hybrid framework system.

Novel open-framework architectures in lanthanide phosphonates

Two novel three-dimensional lanthanide coordination polymers have been prepared hydrothermally with the phosphonic acid N , N ′ -piperazine bis(methylenephosphonic acid), H 2O 3PCH 2N(C 2H 4) 2NCH 2PO 3H 2 ( LH 4). The structures of Gd 2( LH 2) 3⋅3H 2O (I) and Nd 2( LH 2) 3⋅9H 2O (II) have been characterised by single crystal X-ray techniques. One-dimensional ‘lanthanide-phosphate’ chains are a key feature in both structures, although there are major structural differences between the chains, with (I) displaying octahedral GdO 6 coordination and (II) showing eight-coordinate NdO 8 polyhedra. In each case, three-dimensional connectivity is completed by coordination of the phosphonate group resulting in open framework structures encapsulating loosely bound water molecules. Isostructural Y 3+ and Yb 3+ analogues of (I) have been prepared, suggesting that cation size is a key factor in controlling the differing reaction products. In the case of Y 2( LH 2) 3⋅5H 2O, isostructural to (I), it is shown that the extra-framework water molecules may be removed reversibly without framework collapse. Structural relationships to other known lanthanide phosphonates are discussed.

Synthesis and characterization of the novel hydrogen-bonded framework material (C 5H 5NH){AlF[O 3PCH 2PO 2(OH)]}⋅0.61H 2O

The new aluminum diphosphonate, (C 5H 5NH){AlF[O 3PCH 2PO 2(OH)]}⋅0.61H 2O (monoclinic, C 2 / c , a = 18.1898 ( 11 ) Å , b = 10.7396 ( 7 ) Å , c = 12.0022 ( 7 ) Å , β = 105.404 ( 2 ) ° , V = 2260.4 ( 2 ) Å 3 , Z = 8 ), has been synthesized by solvothermal methods and its structure determined using micro-crystal X-ray diffraction data. The material consists of infinite columnar [AlF(O 3PCH 2PO 3)] 2− ∞ anions with chains of cis- and trans- vertex-sharing AlO 4F 2 octahedra at their core. Each methylenediphosphonate group acts as a bisbidentate ligand bonding to adjacent aluminum atoms in a chain, and directly binding to one chain only. The columnar [ AlF ( O 3 PCH 2 PO 3 ) ] 2 − ∞ anions are connected together through hydrogen-bonding interactions to form a hydrogen-bonded framework material containing pyridinium cations and extra-framework water molecules within its channels.

Unusual Coordination Behavior of Cr3+ in Microporous Aluminophosphates

A CrAPO-5 molecular sieve has been investigated with X-ray absorption spectroscopy (EXAFS-XANES) as dehydrated material and after loading with water and ammonia to unravel the coordination geometries of Cr3+ in the framework of a microporous crystalline aluminophosphate, more particularly of the AFI-type. A comparison of the XANES data, a preedge analysis with crystal field multiplet calculations and EXAFS data, pointed toward the presence of framework Cr3+ which, on dehydration, takes on a distorted tetrahedral coordination state. Due to the 3d3 configuration of Cr3+, this unusual tetrahedral coordination environment strongly tends to transform into the more stable 6-fold coordination geometry by binding two extraframework water molecules during hydration. In the presence of ammonia, tetrahedral Cr3+ readily transforms into a 5-fold coordination geometry by binding one ammonia molecule. Therefore, depending on the environmental conditions, the Cr3+ ions can occur in a 4-, 5-, or 6-fold coordination. This observation underlines the flexibility of transition metal ions, such as Cr3+, to cope with unusual coordination geometries in inorganic hosts, making them interesting as potential active sites in heterogeneous catalysis.

Rational design of the pore system within the framework aluminium alkylenediphosphonate series.

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.

Synthesis and Characterization of a Novel Organically Templated Open Framework Zirconogermanate with Three‐ and Seven‐Membered Rings.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and characterization of a novel organically templated open framework zirconogermanate with three- and seven-membered rings.

A new organically templated microporous zirconogermanate, (C(2)H(10)N(2))H(2)O[ZrGe(3)O(9)] (denoted as FDZG-3), with a low framework density of 13.6 T/1000 A(3), has been solvo/hydrothermally synthesized by using ZrO(NO(3))(2).2H(2)O as a zirconium source and triethylenetetramine (TETA) as a structure direct agent. This compound was characterized by means of single-crystal X-ray diffraction analysis, thermogravimetrical analysis, and IR and UV-vis spectra. Its three-dimensional (3D) framework is built up by 1D sinusoidal germanate chains cross-linked by ZrO(6) octahedra, which forms a network containing three- and seven-membered rings (MRs). Four intersecting 7-MR channels can be observed along the b axis, c axis, [110], and [-110] directions, respectively. Charge-balancing (C(2)H(10)N(2))(2+) and extraframework water molecules are encapsulated within 7-MR channels and form hydrogen bonds with framework oxygen atoms. Crystal data for FDZG-3: M = 533.13, monoclinic, space group Cc (No.9), a = 11.299(3) A, b = 7.7649(19) A, c = 13.835(3) A, beta = 104.826(3) degrees, V = 1173.4(5) A(3), Z = 4, R1 = 0.0263, wR2 = 0.0529.

New insights on high-pressure behaviour of microporous materials from X-ray single-crystal data

The main deformation mechanisms induced by pressure on different structural types of zeolites were analysed by comparing experimental data and theoretical models. Data of single-crystal X-ray diffraction obtained with the sample in a Merrill–Bassett diamond anvil cell on a four-circle diffractometer were collected at different pressures for samples of heulandite, scolecite and bikitaite, using non-penetrating pressure transmitting media (glycerol or silicon oil), up to 5 GPa. The results indicated that, at first approximation, the theoretical approach reproduces the structural evolution of zeolites under pressure. However, the flexibility possessed by framework microporous silicates resulted more complex than that which can be modelled by undeformable “rigid-unit modes”, being completely flexible in the oxygen hinges. Moreover, the compressibility of the zeolites under study does not appear to be directly related to the microporosity represented by the framework density (FD): the bulk moduli (simply defined as the inverse of volume compressibility coefficients) of heulandite (27.5(2) GPa) and scolecite (54.6(3) GPa) were different even though their FD’s were quite similar. Single crystal data have shown that the structural evolution of the open-framework silicates, is strongly controlled by the framework, whereas the role of the extra-framework content was less important. In all three zeolites the position of the extra-framework water molecules and cations was maintained approximately and their coordination numbers remained unchanged within the pressure range investigated.