Framework Oxygen Research Articles

Strontium nickel and barium nickel selenites: Synthesis and X-ray diffraction parameters

A new strontium nickel selenite, Sr2Ni(SeO3)3, was prepared and structurally characterized. The compound crystallizes in triclinic system (space group P\( \bar 1 \), a = 7.2860(10) A, b = 7.581(2) A, c = 8.722(2) A, α = 103.02(2)°, β = 105.580(10)°, γ = 95.260(10)°, Z = 2) and is isostructural to cobalt and copper analogues. The structure of Sr2Ni(SeO3)3 is a three-dimensional framework built of eight-vertex polyhedra [SrO8] and distorted octahedra [NiO6] sharing edges and vertices. The framework channels accommodate selenium atoms bonded to the framework oxygen atoms. The selenite groups SeO3 are pyramidal, which is indicative of high stereochemical activity of the Se(IV) lone pair. The possibility of replacement of some Ni atoms by Cu in Sr2Ni(SeO3)3 was studied. The search for analogous barium phases did not reveal such compounds, but BaM(SeO3)2 phases were found, where M = Co, Ni, or Cu. The unit cell parameters of the new selenite BaM(SeO3)2 were determined: space group Pnma, a = 14.989(5) A, b = 5.439(2) A, c = 7.161(3) A, Z = 4.

DFT Calculations of EPR Parameters for Copper(II)-Exchanged Zeolites Using Cluster Models

The coordination environment of Cu(II) in hydrated copper-exchanged zeolites was explored through the use of density functional theory (DFT) calculations of EPR parameters. Extensive experimental EPR data are available in the literature for hydrated copper-exchanged zeolites. The copper complex in hydrated copper-exchanged zeolites was previously proposed to be [Cu(H(2)O)(5)OH](+) based on empirical trends in tetragonal model complex EPR data. In this study, calculated EPR parameters for the previously proposed copper complex, [Cu(H(2)O)(5)OH](+), were compared to model complexes in which Cu(II) was coordinated to small silicate or aluminosilicate clusters as a first approximation of the impact of the zeolitic environment on the copper complex. Interpretation of the results suggests that Cu(II) is coordinated or closely associated with framework oxygen atoms within the zeolite structure. Additionally, it is proposed that the EPR parameters are dependent on the Si/Al ratio of the parent zeolite.

The tert-butyl cation on zeolite Y: A theoretical and experimental study

The structure and energy of the tert-butyl cation on zeolite Y were calculated at ONIOM(MP2(FULL)/6-31G(d,p):MNDO) level. The results indicated that the tert-butyl cation is a minimum and lies between 40 and 51 kJ mol−1 above in energy to the tert-butoxide, depending on the level of calculation. Both species are stabilized through hydrogen bonding interactions with the framework oxygen atoms. Experimental data of nucleophilic substitution of tert-butylchloride and bromide over NaY impregnated with NaCl or NaBr give additional support for the formation of the tert-butyl cation as a discrete intermediate on zeolite Y, in agreement with the calculations.

Synthesis and crystal structure of dehydrated, deaminated, and dealuminated zeolite Y (FAU): single-crystal structure of |Na33H26(Al5O4)|[Si126Al66O384]-FAU

A single crystal of zeolite Y, |Na71|[Si121Al71O384]-FAU, was ion exchanged to generate |(NH4)38Na33|[Si121Al71O384]-FAU. This was then vacuum dehydrated at 673 K, and, without re-exposure to the atmosphere, its structure was determined crystallographically using synchrotron X-radiation in the cubic space group $$ Fd\bar{3} $$ m at 294 K. It was refined to the final error index R 1 = 0.0532 with 522 reflections for which F o > 4σ(F o). The composition (best integers) is determined to be |Na33H26(Al5O4)|[Si126Al66O384]-FAU which means full dehydration, deamination, and dealumination were achieved. The 33 Na+ ions per unit cell were found at two crystallographically distinct positions: nine at site I (in the centers of the D6Rs) and 24 at site II (in supercages opposite S6Rs). The 2.5 sodalite units contained a dimeric tetrahedral aluminate cation (Al–O = 1.40(8) and 1.60(8) A) at its center. Each [Al5O4]7+ cation coordinates to framework oxygen of D6Rs with tetrahedral manner. This work demonstrates that it is possible to obtain large amount of dealuminated species within the H-Y zeolite framework which should enhance the acidity of adjacent sites for higher catalytic activity.

Intrinsic excitons in 12CaO·7Al2O3

Unusual crystal structure of 12CaO·7Al 2 O 3 is composed by a framework of positively charged nanocages, which enable accommodation of various negative ions (and even electrons) inside these cages. Different filling of cages leads to significant changes in electronic structure and as the result in luminescence properties, as well. Luminescence was studied using time-resolved spectroscopy in VUV in the temperature range from 6 to 300 K. Electron loaded samples exhibit UV luminescence band peaked at ∼5 eV. The excitation spectrum of this emission has the onset at the energy gap value of 6.8 eV, and its decay is well described with the sum of two exponential functions with life-times of τ 1 = 3.7 ns and τ 2 = 29 ns, respectively. Its thermal quenching is well approximated by the sum of two Mott-Seitz type curves with the activation energies of 34 meV and 70 meV. Experimental results indicate that this luminescence is possibly due to radiative decay of two singlet self-trapped exciton states, which hole components are localized on two non-equivalent framework oxygens.

TS-1 from First Principles

First principles studies on periodic TS-1 models at Ti content corresponding to 1.35% and 2.7% in weight of TiO(2) are presented. The problem of Ti preferential siting is addressed by using realistic models corresponding to the TS-1 unit cell [TiSi(95)O(192)] and adopting for the first time a periodic DFT approach, thus providing an energy scale for Ti in the different crystallographic sites in nondefective TS-1. The structure with Ti in site T3 is the most stable, followed by T4 (+0.3 kcal/mol); the less stable structure, corresponding to Ti in T1, is 5.6 kcal/mol higher in energy. The work has been extended to investigate models with two Ti's per unit cell [Ti(2)Si(94)O(192)] (2.7%). The possible existence of Ti-O-Ti bridges, formed by two corner-sharing TiO(4) tetrahedra, is discussed. By using cluster models cut from the optimized periodic DFT structures, both vibrational (DFT) and electronic excitation spectra (TDDFT) have been calculated and favorably compared with the experimental data available on TS-1. Interesting features emerged from excitation spectra: (i) Isolated tetrahedral Ti sites show a Beer-Lambert behavior, with absorption intensity proportional to concentration. Such a behavior is gradually lost when two Ti's occupy sites close to each other. (ii) The UV-vis absorption in the 200-250 nm region can be associated with transitions from occupied states delocalized on the framework oxygens to empty d states localized on Ti. Such extended-states-to-local-states transitions may help the interpretation of the photovoltaic activity recently detected in Ti zeolites.

Investigation of Electronic Excitations of Pure and Ce Doped 12CaO•7Al2O3 Using Luminescence Spectroscopy

Pure and Ce doped nanoporous 12CaO•7Al2O3 (C12A7) oxides were synthesized using self-propagating combustion method and solid state reaction. Time-resolved photoluminescence method at low temperatures was applied in studies of powder samples and ceramics, which were obtained in a melt-solidification process partly replacing encaged oxygen ions with electrons. In pure C12A7 with the encaged electrons broad luminescence bands peaked at 3.3 and 5.0 eV were revealed. The first one corresponds to the luminescence due to the encaged oxygen ions and latter one is assigned to the recombination of electrons and holes localized on the framework oxygen ions. Ce doping introduces emission band at 3.0 eV due to 5d-4f transitions with several decay components in nanosecond range. The Ce 5d-4f luminescence is efficiently excited through Ce intra-center absorption as well as through energy transfer processes in the intrinsic absorption region of C12A7 above energy gap at 7.0 eV.

New Insights into ETS-10 and Titanate Quantum Wire: A Comprehensive Characterization

The titanate quantum wires in ETS-10 crystals remain intact during ion exchange of the pristine cations (Na(+)(0.47) + K(+)(0.53)) with M(n+) ions (M(n+) = Na(+), K(+), Mg(2+), Ca(2+), Sr(2+), Ba(2+), Pb(2+), Cd(2+), Zn(2+)) and during reverse exchange of the newly exchanged cations with Na(+). The binding energies of O(1s) and Ti(2p) decrease as the electronegativity of the cation decreases, and they are inversely proportional to the negative partial charge of the framework oxygen [-delta(O(f))]. At least five different oxygen species were identified, and their binding energies (526.1-531.9 eV) indicate that the titanate-forming oxides are much more basic than those of aluminosilicate zeolites (530.2-533.3 eV), which explains the vulnerability of the quantum wire to acids and oxidants. The chemical shifts of the five NMR-spectroscopically nonequivalent Si sites, delta(I(A)), delta(I(B)), delta(II(A)), delta(II(B)), and delta(III), shift downfield as -delta(O(f)) increases, with slopes of 2.5, 18.6, 133.5, 216.3, and 93.8 ppm/[-delta(O(f))], respectively. The nonuniform responses of the chemical shifts to -delta(O(f)) arise from the phenomenon that the cations in the 12-membered-ring channels shift to the interiors of the cages surrounded by four seven-membered-ring windows. On the basis of the above, we assign delta(I(A)), delta(I(B)), delta(II(A)), and delta(II(B)) to the chemical shifts arising from Si(12,12), Si(12,7), Si(7,12), and Si(7,7) atoms, respectively. The frequency of the longitudinal stretching vibration of the titanate quantum wire increases linearly and the bandwidth decreases nonlinearly with increasing -delta(O(f)), indicating that the titanate quantum wire resembles a metallic carbon nanotube. As the degree of hydration increases, the vibrational frequency shifts linearly to higher frequencies while the bandwidth decreases. We identified another normal mode of vibration of the quantum wire, which vibrates in the region of 274-280 cm(-1). In the dehydrated state, the band-gap energy and the first absorption maximum shift to lower energies as -delta(O(f)) increases, indicating the oxide-to-titanium(IV) charge-transfer nature of the transitions.

Synthesis of Tellurium Sorption Complexes in Fully Dehydrated and Fully Ca2+-exchanged Zeolites A and X and their Single-crystal Structures

Single crystals of fully dehydrated and fully Ca 2+ -exchanged zeolites A (|Ca 6 |[Si 12 Al 12 O 48 ]-LTA) and X (|Ca 46 | [Si 100 Al 92 O 384 ]-FAU) were brought into contact with Te in fine pyrex capillaries at 623 K and 673 K, respectively, for 5 days. Crystal structures of Te-sorbed Ca 2+ -exchanged zeolites A and X have been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group Pm3m (a = 12.288(2) A) and Fd 3 (a = 25.012(1) A), respectively. The crystal structures of pale red-brown |Ca 6 Te 3 |[Si 12 A 12 O 48 ]-LTA and black coloured |Ca 46 Te 8 | [Si 100 Al 92 O 384 ]-FAU have been refined to the final error indices of R 1 /wR 2 = 0.1096/0.2768 and R 1 /wR 2 = 0.1054/ 0.2979 with 204 and 282 reflections for which F o > 4σ(F o ), respectively. In the structure of |Ca 6 Te 31 |[Si 12 Al 12 O 48 ]-LTA, 6 Ca 2+ ions per unit cell were found at one crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. In |Ca 46 Te 8 |[Si 100 Al 92 O 384 ]-FAU, 46 Ca 2+ ions per unit cell were found at four crystallographically distinct positions: 3 Ca 2+ ions at Ca(1) fill the 16 equivalent positions of site I, 21 Ca 2+ ions at Ca(2) fill the 32 equivalent positions of site I', 10 and 12 Ca 2+ ions at Ca(3) and Ca(4), respectively, fill the 32 equivalent positions of site II. The Te clusters are stabilized by interaction with cations and framework oxygen. In sodalite units, Te-Te distances of 2.86(10) and 2.69(4) A in zeolites A and X, respectively exhibited strong covalent properties due to their interaction with Ca 2+ ions. On the other hand, in large cavity and supercage, those of 2.99(3) and 2.76(11) A in zeolites A and X, respectively, showed ionic properties because alternative ionic interaction was formed through framework oxygen at one end and Ca 2+ cations at the other end.

Synthesis, structure and absorption spectrum of a new charge transfer salt [Fe(C5H5)2]4H[GeMo12O40] · CH3CN · H2O

A new charge-transfer (CT) salt based on Fe(C5H5)2 and Keggin-type anion [GeMo12O40]4−, [Fe(C5H5)2]4HGeMo12O40 · CH3CN · H2O, was electrochemically synthesized and its structure was determined by single-crystal X-ray diffraction. Triclinic, P1, M = 2668.07, a = 12.600(9) Å, b = 13.033(4) Å, c = 13.298(5) Å, α = 116.312(6)°, β = 101.244(9)°, γ = 92.919(9)°, V = 1896.4(16) Å3, Z = 1, R 1 = 0.0673, wR 2 = 0.1667(I > 2σ). moieties are stacked to form quadrangle channels with distances of and between the cyclopentadienyl rings of two adjacent ferrocene cations along the [0 1 1] direction that accommodate the polyanions, and each polyanion is surrounded by eight adjacent [Fe(C5H5)2]+ units with the nearest distance of framework oxygens of Keggin anions and carbon atoms of [Fe(C5H5)2]+ cations from 2.996 Å to 3.201 Å. The UV–Vis spectrum in concentrated solution indicates the presence of a new band at λ max = 620 nm, ascribed to CT transitions between the ferrocenyl donors and the Polyoxometalate acceptors. IR, EPR, and CV properties of the salts were also discussed.

Behavior of Active Oxygen During the Decomposition of Nitrous Oxide Over Fe-FER

Isotope exchange (I.E) of 18O2 for oxygen captured in Fe-FER after decomposition of nitrous oxide proceeds readily even at room temperature, provided that the amount of surface NOx species, formed as a secondary product of the N2O decomposition, is relatively low. If 18O2 is present during the decomposition of nitrous oxide above 250 °C, or if nitrous oxide labeled with 18O is employed, 18O appears also in NOx species, and I.E easily occurs with zeolite framework oxygens.

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) +.

Molecular adsorption and metal-support interaction for transition-metal clusters in zeolites: NO adsorption on Pdn (n=1–6) clusters in mordenite

The adsorption of NO molecules on Pd(n) clusters of varying size (n=1-6) located in the main channel of mordenite and the interaction of the metallic clusters with the zeolitic framework were investigated using ab initio density-functional calculations under periodic boundary conditions. The supported clusters are created by binding Pd(n) (2+) cations to the inner cavity of a deprotonated Al-exchanged zeolite with an Al/Si ratio of 1/11, such that a charge-neutral system is created. Compared to the highly symmetric structures of the gas-phase clusters, the clusters bound to the zeolitic framework undergo appreciable geometric distortions lowering their symmetry. The distortions are induced by strong interactions with "activated" framework oxygens located close to the charge-compensating Al/Si substitution sites, but the cluster forms also weaker bonds to "nonactivated" oxygen atoms. The interaction with the framework also affects the electronic and magnetic properties of the clusters. While in the gas phase all clusters (except the isolated Pd atom with a closed d(10) ground state) have a paramagnetic moment of 2mu(B), in the zeolite clusters with two to four atoms have zero magnetic moment, while the Pd(5) cluster has a magnetic moment of 2mu(B) and for the Pd(6) cluster, it is even enhanced to 4 mu(B) (but the magnetic energy differences relative to low-spin configurations are modest). Analysis of the magnetization densities shows that in all clusters with zero total moment (singlet ground state), there are sites with excess spin densities of opposite sign. The influence of the cluster-support interaction on the chemical properties of the clusters has been tested by the adsorption of NO molecules. The results demonstrate the interplay between the molecule-cluster and cluster-framework interactions, which can lead to an increase or decrease in the adsorption energy compared to NO on a gas-phase cluster. While on the gas-phase cluster adsorption in low-coordination sites (vertex or bridge) is preferred, for the cluster in the zeolite adsorption in threefold coordinated hollow or twofold bridge sites is preferred. The magnetic properties of the clusters and of the paramagnetic NO molecule play an important role. For the supported clusters with zero magnetic moment, upon adsorption the spin of the molecule is transferred to the cluster (and induces also a modest polarization of the framework). For magnetic clusters, spin pairing induces a reduced magnetic moment of the NO-Pd(n) complex. The redshift of the NO stretching frequencies is reduced compared to the free clusters by the cluster-support interaction for the smaller clusters, while it remains essentially unchanged for the larger clusters. A detailed electronic analysis of the cluster-support interactions and of the adsorption properties is presented.

Adsorption of Benzene to Copper in CuHY Zeolite

Adsorption of benzene to copper-exchanged Y zeolites has been studied employing Fourier transform infrared spectroscopy and QM/MM calculations. Experimentally, both Cu(I) and Cu(II)−Y zeolites were used as adsorbents. Benzene adsorption was observed on both copper and Bronsted acid sites, but the copper site is preferred. The FTIR spectra show the activation of the ν13 in-plane ring stretching mode at 1471 and 1479 cm−1 for Cu and Bronsted sites, respectively. With respect to the gas-phase value, Cu sites cause a red shift of 13 cm−1 whereas Bronsted sites show a shift of 5 cm−1 only. Theoretical investigations were performed on complexes of benzene with Cu-exchanged Y zeolites at two different sites, SII and SIII, with different Si/Al ratios. An η2-coordination of benzene to copper was observed for all adsorption complexes. After adsorption, the 3-fold coordination of Cu to framework oxygens is reduced to 2-fold at site SII, whereas 2-fold coordination prevails at site SIII. Benzene binds with Cu more st...

Structural and property characterization of two new charge-transfer salts based on Keggin ions and ferrocene

Two new charge-transfer salts based on ferrocene and Keggin-type anions, [NBu 4] 6 [Fe(C 5H 5) 2][HAsMo 12O 40] 2 ( 1) and [NBu 4] 2[Fe(C 5H 5) 2] 2[HSiMo 12O 40]·2CH 3CN ( 2), were synthesized and their structures were determined by X-ray diffraction analysis. There are different stoichiometries (Keggin anion: ferrocene cation) in 1 and 2, namely, 2:1 and 1:2. There exist complex interactions between the polyanions, and the framework oxygens of anions and the cyclopentadienyl rings of ferrocene. One of two crystallographic asymmetric Keggin ions in 1 is surrounded by four parallel ferrocene cations with the closest distance of framework oxygens of anions and the cyclopentadienyl rings of ferrocene moiety of 3.16 Ǻ. Each anion in 2 is surrounded by six parallel ferrocene cations with the close distance of framework oxygens of anion and the cyclopentadienyl rings of ferrocene moiety from 3.197 to 3.401 Ǻ. The bond valence sum of Mo atoms in compounds 1 and 2 is in the range of 6.234–6.623 and much larger than 6, which suggests that there is more covalent ingredient between Mo–O in the change-transfer salts owing to the delocalization of one unpaired electron in the reduced Keggin ion. The UV–visible spectra, EPR and CV properties of the salts were also discussed.

Basic catalytic properties of as-synthesized molecular sieves

A series of as-synthesized molecular sieves have been tested and revealed useful as basic catalysts for Knoevenagel condensation under mild conditions. In order to understand the role of the Si/Al ratio, the structure, porosity and template agent, fifteen structures were synthesized and studied in this reaction. Siliceous and large pore molecular sieves showed high conversion levels (97%), while aluminum zeolites, even when containing large amount of organic material, showed distinct activity behavior, which was mainly dependent on the amount of framework silicon. This result, in addition to literature data, indicated that most likely siloxy anions ( SiO −) are the basic active sites. XPS measurements of these hybrid organic–inorganic catalysts showed that O1s binding energy is influenced by the presence of organic template, leading to the conclusion that they are interacting with framework oxygen, possibly balancing framework anions. Calcined siliceous molecular sieves, which had only silanol groups ( SiOH), showed negligible catalytic activity (lower than 2%). As-synthesized siliceous molecular sieves have proven to be useful for basic heterogeneous catalysis, particularly for the synthesis of fine chemicals or for catalytic processes demanding strong basic sites.

Synthesis and crystal structures of two inorganic–organic hybrid vanadium selenites with layered structures: (DABCOH 2)[(VO 2)(SeO 3)] 2·1.25H 2O and (pipeH 2)[(VO) 2(C 2O 4)(SeO 3) 2

The reactions of SeO 2 with V 2O 5 or VOSO 4 in the presence of different organic amine yield two novel vanadium selenites with layered structures, formulated as (DABCOH 2)[(VO 2)(SeO 3)] 2·1.25H 2O 1 (DABCO = 1,4-diazabicyclooctane) and (pipeH 2)[(VO) 2(C 2O 4)(SeO 3) 2] 2 (pipe = piperazidine). Two compounds are characterized with elemental analysis, FT-IR spectrum, TG-DTA analysis and single-crystal X-ray diffraction analysis. In compound 1, two symmetry-related VO 6 units share an edge to form a [V 2O 6] cluster. Each [V 2O 6] cluster is bridged by four SeO 3 units to generate a two-dimensional grid structure. In compound 2, VO 6 units and SeO 3 units share corners to result in a ladder motif. Adjacent chains are interlinked by the oxalate ligands, creating a 2D brick-wall structure, which is firstly observed in V/Se/O system. Diprotonated DABCO and lattice water molecules in 1 and diprotonated piperazidine molecules in 2 are located in the interlayer regions and interact with the framework oxygen atoms via hydrogen bonds, respectively.

Cation distribution in K,H-L zeolite prepared through ion-exchange with TMA ion

Structural analyses of hydrated K 9-L and K 7.5H 1.5-L zeolites were carried out by measurements of X-ray powder diffraction patterns and Rietveld refinements, and distributions of potassium ion in the zeolites were investigated. K 7.5H 1.5-L was obtained by heating K 7.5TMA 1.5-L at 773 K in air, which was prepared through an ion-exchange of K 9-L with TMA ion. In both K 9-L and K 7.5H 1.5-L, potassium ion located only on sites B, D and E. The number of potassium ion on site D was the most remarkably different between K 9-L and K 7.5H 1.5-L, that is, its number was 4.08 per unit cell (puc) in K 9-L and 3.00 puc in K 7.5H 1.5-L. It was found from this result that TMA ion preferentially exchanges with potassium ion on site D. The potassium ion on site E also reduced to 2.52 puc in K 7.5H 1.5-L from 2.94 puc in K 9-L. It was considered that the reduction arose in the ion-exchange between K +/E and the hydrogen ion (just) after converting to K,H-L from K 7.5TMA 1.5-L by heating, because TMA ion cannot access site E at all due to the location of site E and its ion size, but hydrogen ion can. All the nearest interatomic distance between a potassium ion and a framework oxygen showed the tendency which becomes longer in K 7.5H 1.5-L than K 9-L. The results suggest that the Coulmbic attraction between the potassium ion and a negative chare of framework ( AlO 4 − ) becomes weaker in K 7.5H 1.5-L than K 9-L.

Anion diffusion processes in O- and N-mayenite investigated by neutron powder diffraction

The crystal structure of mayenite (ideal composition: Ca12Al14O33) consists of a (disordered) calcium-aluminate framework comprising 32 of the 33 oxygen anions. It contains large open cages, 1/6 of them being filled randomly by the remaining “free” oxygen which is available for diffusion and very high ionic conductivities. This extraframework oxygen could be substituted by nitrogen, opening up possibilities for a pure nitrogen ionic conductor. From high temperature neutron powder diffraction experiments, data analysis employing difference Fourier methods and anharmonic Debye-Waller factors and comparing pure O-mayenite with partly exchanged N/O-mayenite it is concluded that oxygen diffusion proceeds via jump-like processes, intimately coupled to relaxations of Ca and involving exchange of the “free” oxygen with framework oxygen, while nitrogen diffusion appears to proceed via an interstitial process.

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.