Framework Oxygen Atoms Research Articles

Understanding the Reactivity and Basicity of Zeolites: A Periodic DFT Study of the Disproportionation of N2O4 on Alkali-Cation-Exchanged Zeolite Y

The disproportionation of N(2)O(4) into NO(3)(-) and NO(+) on Y zeolites has been studied through periodic DFT calculations to unravel 1) the role of metal cations and the framework oxygen atoms and 2) the relationship between the NO(+) stretching frequency and the basicity of zeolites. We have considered three situations: adsorption on site II cations with and without a cation at site III and adsorption on a site III cation. We observed that cations at sites II and III cooperate to stabilize N(2)O(4) and that the presence of a cation at site III is necessary to allow the disproportionation reaction. The strength of the stabilization is due to the number of stabilizing interactions increasing with the size of the cation and to the Lewis acidity of the alkali cations, which increases as the size of the cations decreases. In the product, NO(3)(-) interacts mainly with the cations and NO(+) with the basic oxygen atoms of the tetrahedral aluminium through its nitrogen atom. As the cation size increases, the NO(3)(-)...cation interaction increases. As a result, the negative charge of the framework is less well screened by the larger cations and the interaction between NO(+) and the basic oxygen atoms becomes stronger. NO(+) appears to be a good probe of zeolite basicity, in agreement with experimental observations.

The cleavage of the methane C [sbnd]H bond over PdO/H-BEA: A density functional theory study

Cluster models were used to represent the β-type cationic sites of the protonated beta zeolite (H-BEA) and the loading of PdO on these sites. The properties of these clusters and the cleavage of methane C H bond over these clusters were studied using density functional theory (DFT) method. The stability of H-BEA was enhanced due to the formation of hydrogen bonds. After PdO loading, the Pd atom bonds to four oxygen atoms among which three H-BEA framework oxygen atoms are included to form an approximate planar structure with Pd in the centre. This structure is very similar to that of bulk PdO. The acidic proton of H-BEA and the oxygen atom of PdO participate in the cleavage of methane C H bond, indicating that PdO is the active species for the activation of methane. Over the clusters constructed in the present work, the calculated energy barriers for the cleavage of methane C H bond are in the region between 17.54 and 21.02 kcal mol −1.

Pressure-Induced Hydration and Order−Disorder Transition in a Synthetic Potassium Gallosilicate Zeolite with Gismondine Topology

Two high-pressure phases of a potassium gallosilicate with a gismondine framework (K-GaSi-GIS) were characterized using Rietveld refinements of in-situ high-pressure, high-resolution synchrotron X-ray powder diffraction data. The observed response of the K-GaSi-GIS framework under hydrostatic pressure is a gradual flattening of the so-called "double crankshaft" structural chain units. At pressures below 1.0(1) GPa, additional water molecules from the hydrostatic pressure-transmitting medium are inserted into the potassium-water guest network ("pressure-induced hydration") resulting in a "super-hydrated" high-pressure phase I. As the flattening of the double crankshaft structural units in the GIS framework continues above 1.6 GPa, the ellipticity of the cross-linking 8-ring windows is reduced below a certain threshold, and a disordering of the potassium-water guest structure along the 8-ring channel, characteristic of a disordered high-pressure phase II, is observed. The concerted framework distortion and guest network disordering accommodates the increased hydration level while maintaining the seven-fold coordination environment of the potassium cations to framework oxygen atoms and water molecules. We have thus established the atomistic details of a guest-host order-disorder transition under pressure-induced hydration conditions in a zeolite with GIS framework and compared it to other zeolites during pressure-induced hydration. We find that the structural changes mediated by the extra-framework cations and their coordination environment under PIH conditions are at the core of these different mechanisms and are driving the changes in the ellipticity of pore openings, order-disorder and disorder-order transitions, and framework distortions.

High pressure deformation mechanism of Li-ABW: Synchrotron XRPD study and ab initio molecular dynamics simulations

The response to compression of the synthetic zeolite Li-ABW (LiAlSiO 4 · H 2O, Z = 4, s.g. Pna2 1) was explored by synchrotron X-ray powder diffraction experiments, using silicone oil as non-penetrating pressure transmitting medium, and Car Parrinello Molecular Dynamics simulations. In the range P amb – 8.9 GPa, a nearly isotropic compression for the axial parameters and a cell volume decrease of approximately 12% are observed. A discontinuity in the cell parameters vs P behaviour can be detected between 5 and 6 GPa. As a consequence, the bulk modulus was calculated separately in the P amb – 4.9 GPa and 5.6–8.9 GPa pressure ranges. The corresponding values (72(2) GPa and 80(2) GPa, respectively) are among the highest found up to now for zeolites studied with non-penetrating P-transmitting media. Molecular Dynamics simulations were performed at volumes corresponding to P amb, 1.5, 5.6, and 7.6 GPa, respectively. At 1.5 GPa the channel system is already elliptically deformed, and the zig-zag trend of the 4-ring tetrahedral chains is enhanced. Moreover, the water molecule chain running along the channel becomes interrupted and the water molecules are more strongly connected to the framework oxygen atoms. The four-fold coordination of Li cation is maintained up to the highest pressure and only a slight bond distance decrease is observed above 1.5 GPa. In the P amb – 5.6 GPa range, all T–O–T angles decrease with pressure, and hence the Li-ABW structure can be defined as collapsible. Otherwise, at higher compression, average T–O–T angles increase slightly. Overall, the deformation of the Li-ABW upon compression resembles that achieved by anhydrous Li-ABW in the high temperature regimes.

Interaction of acetonitrile with Na-zeolites: adsorption modes and vibrational dynamics in the zeolite channels and cavities

The interaction of acetonitrile with the extra-framework Na(+) cations in zeolites, namely Na-LTA and Na-FER, was investigated. The relative stabilities of possible types of adsorption complexes were calculated at the periodic DFT level. Individual effects on the complex stability and on the vibrational dynamics of adsorbed acetonitrile were qualitatively analysed on various cluster models. The acetonitrile primarily interacts with the Na(+) cation (via the N end), and the complex stability is modulated by the interaction of the methyl group with the framework oxygen atoms, which has a partial hydrogen-bond character. In line with the results of recent analyses of CO interactions with metal-exchanged zeolites [D. Nachtigallová, O. Bludský, C. O. Areán, R. Bulanek and P. Nachtigall, Phys. Chem. Chem. Phys., 2006, 8, 4849], two types of effects should be taken into consideration for acetonitrile complexes in Na-zeolites: (i) the effects from the bottom, reflecting the accessibility and coordination of the primary metal cation, to which the acetonitrile molecule is bonded via the N atom; and (ii) the effects from the top, including H-bond formation (stabilising effect) or repulsion due to the secondary metal cation. The effect from the bottom results in a blue shift of nu(CN) while the effect from the top (H-bond formation) results in a red shift in both nu(CN) and nu(CH).

菱沸石の結晶構造精密化―水分子と交換性陽イオンの結晶学的配置―

Locations of water molecules and exchangeable cations in a hydrated natural chabazite with a composition of Ca1.57Na0.49 [Al3.39Si8.55O24] ⋅12.47H [d2] O were successfully determined by single crystal X-ray diffraction. The structure analyses have revealed the presences of five partially occupied water sites (OW1-OW5) and four partially occupied exchangeable-cation sites (Ca1-Ca4), and have showed that fully coordinated exchangeable cations can adopt sixfold or sevenfold coordination. The distances between water sites and framework oxygen sites and between water sites suggest that the hydrogen bonds formed between water molecules and framework oxygen atoms are very weak, whereas strong hydrogen bonds exist between water molecules.

Are carbenium and carbonium ions reaction intermediates in zeolite-catalyzed reactions?

The mechanism of acid-catalyzed hydrocarbon reactions such as skeletal isomerization, hydride transfer, alkylation, dehydrogenation and cracking in superacid media and over solid zeolites is analyzed and compared. In particular, the stability, rearrangements and nature (reaction intermediates or transition states) of trivalent carbenium ions and non-classical pentacoordinated carbonium ions in homogeneous and heterogeneous phase are discussed. It is concluded that both carbenium and carbonium ions may exist as true reaction intermediates in zeolite-catalyzed processes only when the positive charge is not easily accessible to framework oxygen atoms.

A DFT–ONIOM study on the effect of extra-framework aluminum on USY zeolite acidity

Abstract The effect of Al(OH) 2 + EFAL (extra-framework aluminum) species in the acid strength of USY zeolite was studied by the ONIOM scheme, at PBE1PBE/6-31G(d,p) level. The model consists of a hexagonal prism and the sodalite cage (T 30 ), representing a real part of the zeolite Y system that allows calculation of different acid sites (O 1 and O 3 ). The acid strength was calculated by computing the deprotonating energy and comparing the results with the data obtained for an isolated acid site. The calculations indicated that there occurs an increase in acid strength, depending on the relative position between the EFAL and the acid site. However, the role of Al(OH) 2 + EFAL is not to increase the energy of the acid form, through Brϕnsted/Lewis synergism, but to stabilize the conjugated base, formed upon deprotonation, by hydrogen bonding and nucleophilic interaction with the framework oxygen atom.

Role of Electrostatic Effects in the Pure Component and Binary Adsorption of Ethylene and Ethane in Cu-Tricarboxylate Metal-Organic Frameworks

The interaction of ethane and ethylene with a Cu-tricarboxylate complex was investigated, showing that at low loadings the lighter molecule has a higher binding energy as a result of interaction with framework Cu and H-bonding with basic framework oxygen atoms. This leads to the selective adsorption of ethylene at low pressure by a factor of ca. 2. This is overcome by the stronger van der Waals interaction of ethane at high loadings, explaining recent literature data. Both experimental data and single-component Grand Canonical Monte Carlo (GCMC) simulations were fitted well with the Unilan model and mixture isotherms were satisfactorily predicted by the Ideal Adsorbed Solution Theory when compared with binary simulation results. Both binary GCMC simulations and Ideal Adsorbed Solution Theory predictions yielded separation factors of ca. 2 and a difference in isosteric heat of 3 kJ/mol. The results suggest that the Cu-BTC framework offers a possible route for the separation of ethane and ethylene, a Holy Grail of adsorption.

Crystallographic Determination of the Positions of the Copper Cations in Zeolite MFI

Copper-exchanged Cu−MFI (Cu−ZSM-5) materials have been prepared by reacting H−MFI samples with 0.1 M Cu(II) acetate solutions. Interpretation (Rietveld method) of X-ray powder diffraction (XRPD) profiles corresponding to two fully dehydrated Cu−MFI phases, reveals the presence of several independent extra framework Cu centers. In H1.04Cu(I)1.19Cu(II)0.51MFI and H1.99Cu(I)2.37Cu(II)0.00MFI, four and five Cu cations are located, respectively. In these two phases, the Cu1/Cu2/Cu2‘/Cu3/Cu3‘ populations are 0.0/1.07/0.02/0.17/0.45 and 0.18/1.12/0.44/0.20/0.50 per unit cell (uc), respectively. Cu2 is the most populated one. The shortest distances between copper sites and framework oxygen atoms involve the Cu1, Cu2, and Cu2‘ sites (Cu−O in the 1.99−2.32 Å range). The Cu1, Cu3, and Cu3‘ sites are trapped in secondary five and six ring channel sections of the MFI framework. Cu2 and Cu2‘ are very close to the 10-membered rings of the straight channel sections. One or both of these cations, which are immediately accessible to guest molecules, appear to be the prime candidates for the catalytically active sites in copper-exchanged MFI.

Cronstedt’s zeolite

Abstract Axel F. Cronstedt (1722–1765), famous Swedish mineralogist, was the first scientist to describe, 250 years ago, the distinctive property of zeolites, i.e., the unique frothing characteristics when heated in a blow-pipe flame. Cronstedt examined two specimens: one from Svappavaara in Northern Sweden and one that was said to come generically from Iceland. From Cronstedt’s indications, the occurrence of the first specimen was near the mining area of Kiruna. The morphological characteristics of the specimen suggested that the zeolite species is stilbite which would make it the first discovered zeolite mineral. This paper is devoted to the description of the structure and microstructure of that first discovered natural zeolite from Svappavaara (Northern Sweden). The SEM investigation of all the sample rock cavities filled with the zeolite crystals and the optical observation of the separated zeolite crystals revealed that the sample is mainly composed of stellerite with subordinate stilbite crystals which are present only in a few cavities together with stellerite. The chemical formula of the stellerite crystals derived from the EPMA and TG analyses is (Ca4.03Mg0.01Na0.03K0.11) [Si27.81Al8.19O72]·28.6H2O. The results of the structure refinement confirm that the investigated specimen is actually stellerite and evidenced no ordering in the tetrahedral sites. The structure refinement evidenced no ordering in the tetrahedral sites. The extraframework cation Ca is located in the centre of the main channel parallel to the a axis, on the mirror plane and is surrounded by water molecules with no contact with framework oxygen atoms. The coordination of Ca is 6-fold. A number of short water–water distances are possible by considering the different possible schemes around the Ca atom. Considering the short water–water distances and the partial occupancy of water sites, a number of octahedral coordinations around Ca are possible.

Confined Water Clusters in a Synthetic Rubidium Gallosilicate with Zeolite LTL Topology

A rubidium gallosilicate with zeolite LTL framework topology has been synthesized under hydrothermal conditions, and the as-synthesized hydrated material was characterized via high-resolution synchrotron X-ray powder diffraction at room temperature. Rb-GaSi-LTL, Rb9.8Ga10.4Si25.6O72·17.5H2O, is hexagonal, space group P6/mmm, with a = 18.6260(1) Å and c = 7.6459(1) Å. The framework model shows complete disordering of Ga and Si in the tetrahedral sites, which is analogous to the framework chemistry of its potassium counterpart, K11Ga10.3Si25.7O72·15.1H2O with a = 18.5525(1) Å and c = 7.5619(1) Å, but contrasts to the proposed preferential aluminum partitioning for the 6-ring sites in the aluminosilicate analogues. Similar to the cation distribution in the potassium analogue, half of the rubidium cations in the unit cell fully occupy the sites associated with the narrow channels on the z = 1/2 plane (sites B and C), whereas the other half fill, on average, five out of the six 8-ring sites in the recessed walls of the main 12-ring channel on the z = 0 plane (site D). All of the water molecules are located along the main 12-ring channels at z = 0, 1/6, 1/3, and 1/2 planes. Water molecules on the latter three planes form clusters within the 12-ring windows confinement via hydrogen bonding to one another and to framework oxygen atoms, while those on the z = 0 plane separate the water clusters by coordinating to the site D cations in the main channel. This partitioning of water molecules in the main channel becomes modulated in the hydrated potassium analogue and seems to be dependent on the chemistry of non-framework cations.

Adsorption of carbon monoxide on Li-ZSM-5: theoretical study of complexation of Li+ cation with two CO molecules

The Li+ cation complexes with one and two CO molecules have been studied computationally. The calculations reveal the conditions when two CO molecules could bind to one Li+ cation in zeolite Li-ZSM-5. In the absence of dicarbonyls (at low adsorbate coverage or at high temperatures), the IR absorption bands can be assigned only on the basis of the Li+ coordination number to the framework oxygen atoms.

Crystallographic configurations of water molecules and exchangeable cations in a hydrated natural CHA-zeolite (chabazite)

Crystallographic configurations of water molecules and exchangeable cations in a hydrated natural CHA-zeolite (chabazite) with a composition of (Ca 1.57Na 0.49)(Al 3.39Si 8.55)O 24 · 12.47H 2O have been examined from the structure analyses based on single-crystal X-ray diffraction data. The structure analyses have revealed the presence of five partially occupied water sites (OW1–OW5) and four partially occupied exchangeable-cation sites (Ca1–Ca4), and the final structure refinement converged to R = 0.0283 and R w = 0.0276 for 1255 reflections. Of these sites, the Ca4 and OW2 sites are located at the center of the [4 66 2]-ring and the center of the 8-ring window in the [4 126 28 6]-cavity, respectively, and the remaining sites are inside the [4 126 28 6]-cavity. The Ca1 atoms can be coordinated only by water molecules, and fully coordinated Ca1 atoms can adopt an octahedral coordination or a triangular-prismatic coordination depending on configurations of water molecules. The Ca2 and Ca3 atoms can be coordinated by both framework oxygen atoms and water molecules, and fully coordinated Ca2 and Ca3 atoms can adopt a sevenfold coordination and an octahedral coordination, respectively. The Ca4 atoms are coordinated octahedrally by six framework oxygen atoms. Judging from OW⋯O and OW⋯OW distances, the hydrogen bonds formed between water molecules and framework oxygen atoms are expected to be very weak, whereas strong hydrogen bonds can exist between water molecules.

The structure of K-hydrosodalite

Hydrosodalite, Na 6[AlSiO 4] 6 · 8H 2O, is a synthetic modification of natural sodalite with water molecules replacing for the anion at the centre of the β cage. Hydrosodalite has a cubic structure with space group P 4 ¯ 3 n and a ≈ 8.9 Å. Cation ordering and framework distortions leading to symmetry reduction were observed for synthetic sodalites but have never been reported for hydrosodalite. This work reports the first experimental evidence of a symmetry reduction in hydrosodalite. The investigated sample is a K-exchanged hydrosodalite with chemical formula K 6[AlSiO 4] 6 · 7.8H 2O. The structure refinement was performed using synchrotron powder diffraction data in space group P1 with a = 9.196(1) Å, b = 9.188(1) Å, and c = 9.205(1) Å, α = 89.69(1)°, β = 90.43(1)°, and γ = 89.791(9)°. K + strongly interacts with all the framework oxygen atoms of the hexagonal ring and provokes anisotropic distortion of the framework. In the distorted framework, the only possible distribution scheme for the K + ions is ordered, to prevent any Coulomb repulsion between adjacent ions. In addition, the ordered scheme is the only to ensure even distribution of the positive cation charges with respect to the Al atoms (Al:K ratio is 1:1). In fact, each of the six Al atoms has three K + ions at a distance of 3.5–3.9 Å and in turn, each of the six K + ions has three Al atoms at a distance of 3.5–3.9 Å. K + ions display a coordination number from 8 to 10 and mean K–O distance, including the water molecules, of 2.921–3.043 Å.

Structure of the hydrated pyrochlore NaW 2O 6· nH 2O

The structure of the non-stoichiometric pyrochlore NaW 2O 6· nH 2O has been refined from powder neutron diffraction data using the Rietveld method. The stoichiometry found from the structural refinements is Na 0.85(2)W 2.02(2)O 6·0.92(5)H 2O in good agreement with other analytical studies. The Na cation is seven-coordinated bonding to six framework oxygen atoms and one oxygen atom from the water. The refinements show a disordered H 2O molecule to be present with the O(2) on a 32e site and the H(1) 48f site.

Rietveld structure refinement of NH4-exchanged natural chabazite

In this work the results of the X-ray Rietveld structure refinement of a natural and the corresponding NH 4 -exchanged chabazite from Nova Scotia (Canada) are exposed. Experimental data were collected using a laboratory powder diffractometer equipped with copper tube and graphite crystal monochromator. The outcome of this crystal-structure study is useful for (i) understanding the structure modifications induced by the NH 4 + exchange; (ii) understanding the physical-chemical and technological properties of NH 4 -chabazite, a zeolite vastly used for industrial applications; (iii) understanding the mechanism of proton conductivity of the NH 4 -exchanged zeolites, precursors of catalytically active H + forms. The position and orientation of the NH 4 + ion were initially refined using the rigid body model and later with the aid of soft constraints. The coordination number of the ammonium ion is 9 with two equally possible and mutually exclusive configurations. One coordination environment includes 3 oxygen atoms O3, 3 oxygen atoms O4, and 3 H 2 O molecules W2a. The other environment includes 3 oxygen atoms O3, 3 oxygen atoms O4, and 3 H 2 O molecules W3. As already shown for other NH 4 -zeolites, the N-O distances are larger than the N-H 2 O distances. The local geometry of the ammonium ion points to a monodentate configuration. A bidentate configuration of the hydrogen bonds for NH 4 + is also possible if the long H2…O3 separation is considered to be at bond distance. For industrial and technological applications, knowledge of the local environment of NH 4 + in the cavities of zeolites is important. Weak hydrogen bonds with framework oxygen atoms implies that the ammonium molecule can be easily exchanged or desorbed. This property is attractive for agronomy, horticulture and soil remediation where zeolite can be added to chemical fertilizers to improve the soil9s chemical and physical properties for plant growth, to increase fertilizer efficiency and to reduce the leaching of nutrients, to reduce the dissolution rate of a soluble fertilizer via ion exchange or combination of mineral dissolution and ion exchange, and to act as remediation agents in soils.

Synthesis, characterization and catalysis of (Co, V)-, (Co, Cr)- and (Cr, V)APO-5 molecular sieves

A series of MAPO-5 and (M, N)APO-5 (with M and N = Co 2+, Cr 3+ and V 4+) molecular sieves have been hydrothermally synthesized and characterized. The as-synthesized and calcined samples were investigated with XRD, ICP, DRS UV–vis spectroscopy, ESR, 27Al MAS NMR techniques to explore the valence, coordination and location of the incorporated transition metal ions. It was shown that isomorphous substitution of Co 2+ for Al 3+ convincingly occurred, and V 4+ also anchored to the sample by coordinating to two framework oxygen atoms and most probably occupying P 5+ sites, while no unambiguous spectroscopic evidence was provided for the incorporation of Cr 3+ in the lattice, although chemical analysis suggests this possibility in the case that Co 2+ or V 4+ are added to the synthesis gel. The preferential sequence for the incorporation of these transition metal ions in the AFI framework is: Co 2+ > V 4+ > Cr 3+. After calcination, almost all V 4+ ions were oxidized to V 5+, whereas Cr 3+ ions were oxidized to Cr 5+ and Cr 6+. As catalysts, the (M, N)APO-5 molecular sieves are highly active for the selective oxidation of cyclohexane with a high cyclohexanone/cyclohexanol ratio in the presence of H 2O 2. The reaction temperature and solvent significantly influenced the catalytic behavior. Although some leaching of the transition metal ions was observed, the catalytic performance remained stable at least within five repeated runs.

Adsorption and Photophysics of Fullerene C60 at Liquid−Zeolite Particle Interfaces: Unusually High Affinity for Hydrophobic, Ultrastabilized Zeolite Y

Adsorption of fullerene C60 from solution to the external surface of zeolite particles has been investigated. The most intriguing result of this study was the nature of C60 adsorption to ultrastablized zeolite Y (or USY). Two commercial samples of USY were tested: CBV780 (Y780) and CBV901 (Y901). Y901 was shown in previous reports to be more hydrophobic than Y780. Higher affinity of C60 for Y901 was found relative to Y780 in a variety of hydrocarbon solvents, including toluene and cyclohexane. In these same solvents, weak or no affinity for Y901 of typical arenes such as naphthalene or pyrene was observed. In toluene, adsorption isotherms for C60 gave dissociation constants (and values of saturation binding) = 0.5 microM (5.8 micromol g(-1)) and 8 microM (1.4 micromol g(-1)) for Y901 and Y780, respectively. C60 was estimated to cover nearly one-half of the estimated external surface area of Y901 particles at saturation. Significant adsorption of C60 to the ionic zeolites NaX, NaY, and KL was observed in cyclohexane but not in toluene, consistent with the pi-cation effect as a driving force for adsorption to these materials. The main driving force for C60 adsorption to Y901 is postulated to involve the interaction of C60 with lone pair electrons of framework oxygen atoms of the 12-ring entry aperture to the supercage. In the 12-ring site, C60 is located in half-supercage bowls on the exterior particle surface. The adsorptive interaction on Y901 relies on the spherical shape of C60 and the hydrophobicity of the zeolite surface. On ionic zeolites, the presence of specific adsorption sites such as exchangeable cations and hydroxyl groups hinder the special positioning necessary for C60 interaction with the 12-ring site. The ground-state and triplet-state absorption spectrum of adsorbed C60 was solution-like on all zeolites. Quenching of the C60 triplet state was examined by using transient absorption spectroscopy. Rate constants for quenching by rubrene, ferrocene, and O2 at the Y901-toluene interface were 18, 9, and 3 times lower, respectively, relative to rate constants in solution. These differences point out that the approach of molecular quenchers to C60 at the interface is more hindered for larger molecules, an expected result for C60 located in half-supercage bowls. The high affinity of fullerenes for hydrophobic zeolite Y provides a strategy for organizing fullerenes at interfaces and for studies of fullerene photochemistry.

Theoretical investigation of site-specific characteristics of CO adsorption complexes in the Li +-FER zeolite

The coordination of extraframework Li + cations in FER and the formation of mono- and dicarbonyl complexes in the Li +-FER zeolite were investigated using a periodic density function theory (DFT) model. The Li + cations strongly prefer the coordination on top of five- or six-member rings on the channel wall. The Li + cation is always coordinated to at least three framework oxygen atoms. Calculated CO stretching frequencies are in excellent agreement with experimental results [Microporous Mesoporous Mater. 34 (2000) 67]; thus, the interpretation of experimental data at the atomic scale level is proposed. The dicarbonyl complexes can be readily formed on Li + cations coordinated in the eight-member ring entrance window of perpendicular channel. The differences in IR spectra of CO adsorbed on Li +-FER and Li +-MFI zeolites can be understood based on the theoretical investigation. The IR band at 2193 cm −1 observed for CO/Li +-MFI system but missing in the IR spectra of CO/Li +-FER is due to the Li + sites on the channel intersection where Li + is coordinated only to two oxygen atoms of AlO 4 tetrahedron. While such sites are populated in Li +-MFI they are not significantly populated in Li +-FER. Therefore, the differences in vibrational dynamics of CO adsorbed on Li + in FER and MFI are due to the differences in Li + coordination in these frameworks.