Location and orientation of adsorbed molecules in zeolites from solid-state REAPDOR NMR

Holland, Gregory P.; Alam, Todd M.

doi:10.1039/b418943d

“…19-20 27 Al SSNMR experiments have proven to be a valuable structural probe of MIL-53, since 27 Al NMR parameters are highly sensitive to the symmetry and coordination of the local Al environment. 27 Al SSNMR experiments may be used to investigate of the short-range structure and order in porous materials such as zeolites [21][22][23][24] and MOFs. 15,[25][26][27][28] In particular, 27 Al SSNMR has been utilized to gain rich information regarding the local aluminum environment within the various forms of MIL-53, 8,29-31 as well as MIL-53 loaded with nitrogen bases and o-xylene.…”

Section: Introductionmentioning

confidence: 99%

Investigating adsorption of organic compounds in metal-organic framework MIL-53

Ibrahim

¹

,

Xu

²

,

He

³

et al. 2015

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Metal-organic frameworks (MOFs) are versatile materials that incorporate metal centers along with organic linkers in highly ordered, intricate structures. MIL-53 is a MOF that exhibits a "breathing effect," where the pore size and MOF topology are profoundly influenced by the identity and binding mechanism of guest molecules. This phenomenon renders MIL-53 a promising candidate for sensing applications. In this report, the adsorption of various organic compounds within MIL-53 is investigated using a combination of complementary techniques. Thermal gravimetric analysis experiments confirm loading of the guest molecules and yield insight into adsorption interactions and strengths. Significant guest-induced changes in the crystal structure of MIL-53 are revealed by powder X-ray diffraction experiments; specific unique phases of MIL-53 are related to the identity of the guest molecule and its binding mechanism to the framework. 27 Al and 13 C solid-state NMR experiments probe the interaction between guest molecules and MIL-53. The relationship between the nature of the guest, the structure of MIL-53, and 27 Al NMR parameters is explored. 27 Al NMR parameters are sensitive to the host-guest binding mechanism (i.e., hydrogenbonding or -stacking interactions) and yield valuable information regarding the influence of the adsorbates on the local aluminum environment. This combination of physical characterization techniques is a useful probe of guest adsorption and the breathing effect within MIL-53 and should prove useful for investigation of related MOFs. Résumé: Les réseaux métallo-organiques (MOF, acronyme anglais pour Metal-Organic Frameworks) sont des matériaux polyvalents où des centres métalliques sont incorporés dans un réseau organique formant des structures complexes et hautement ordonnées. Le MIL-53 est un réseau métallo-organique présentant un « effet de respiration », dont la taille des pores et la topologie du réseau métallo-organique dépendent fortement de l'identité et du mécanisme de liaison des molécules invitées. Ce phénomène fait du MIL-53 un candidat prometteur pour des applications dans le domaine des capteurs. Dans les présents travaux, nous avons étudié l'adsorption de divers composés organiques au MIL-53 à l'aide d'un ensemble de techniques complémentaires. Des analyses thermogravimétriques confirment la charge de molécules invitées et fournissent un aperçu des interactions et des forces d'adsorption. Des expériences de diffraction des rayons X sur poudre ont permis de révéler des modifications importantes de la structure cristalline du MIL-53 induites par l'invité; des phases uniques propres au MIL-53 sont liées à l'identité de l'invité et à son mécanisme de liaison au réseau. Des expériences de RMN 27 Al et 13 C à l'état solide ont permis d'explorer les interactions entre les molécules invitées et le MIL-53. Nous avons étudié la relation entre la nature de l'invité, la structure du MIL-53 et les paramètres RMN 27 Al. Ces derniers sont sensibles au mécanisme de liaison hôte-invité (c.-à -d. les l...

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“…This distance of 1.8 A ˚is indicative of a hydrogen bond between ammonia and the framework, and is in agreement with previous NMR studies. 16,39 Fig. 3 shows the calculated INS spectra for these NaAÁxNH 3 systems.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies that satisfy these criteria mainly center around magnetic resonance techniques. 15,16 Elucidation of local structure by NMR may become difficult in the presence of strongly paramagnetic centres, such as may exist in d-and f-block exchanged zeolites, and thus the application of techniques that are independent of electron/spin density to such systems would be beneficial. INS has previously been used to examine the vibrational modes of organic molecules within zeolite cages, [17][18][19] and we note that INS spectra are easily manipulated making the removal of a background (in our case that of the sample container and the zeolite pre-ammoniation) trivial.…”

Section: Introductionmentioning

confidence: 99%

Inelastic neutron scattering of Na-zeolite A with in situ ammoniation: an examination of initial coordination

Seel

¹

,

Sartbaeva

²

,

Rammirez-Cuesta

³

et al. 2010

Phys. Chem. Chem. Phys.

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The detection and rationalization of the coordination of low concentrations of ammonia within Na-zeolite A is carried out by the application of inelastic neutron scattering (INS), using inverse geometry time of flight spectrometry to study the partial phonon density of states of in situ ammoniated Na-zeolite A. The experimental spectra are subsequently characterised by density functional calculations, incorporating pre-optimisation by geometric simulation. We find that at a concentration of four ammonia molecules per alpha-cage, the ammonia molecule coordinates with extra-framework Na(+) cations and gives rise to three structured regions in the INS spectrum. We show that these regions correspond to translational, librational and tilting motions of the ammonia molecule. These results are in agreement structurally with previous studies of ammonia within a zeolite, and thus show that INS is a valid technique for such investigations.

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“…In catalyzed oxidation reactions, the question of the role of catalyst's oxygen in the interaction with oxidants, as well as the possible role of oxygen mobility for surface and bulk diffusion, can be answered by using 18 O substitution. 5 [155], 15 N-pyridine [156], and 15 N-labeled di-tert-butylpyridine [157] as probe molecules for the characterization of acid sites on zeolite and sulfated zirconia catalysts. 5 [155], 15 N-pyridine [156], and 15 N-labeled di-tert-butylpyridine [157] as probe molecules for the characterization of acid sites on zeolite and sulfated zirconia catalysts.…”

Section: Oxygen Isotopes ( 17 O 18 O)mentioning

confidence: 99%

Isotopic Labeling and Kinetic Isotope Effects

Bauer

¹

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Synthesis and Analysis of Labeled Compounds Kinetic Isotope Effects Applications of Labeled Compounds Carbon Isotopes ( 11 C , 13 C , 14 C ) A Methanol‐to‐Gasoline Reactions; Methylation of Olefins and Aromatics B Isomerization of Alkylaromatics C Isomerization of Olefins and Paraffins D Paraffin Dehydrocyclization E Coke Formation Hydrogen Isotopes ( 2 H , 3 H ) A H / D Exchange of Hydrocarbons over Metal and Acid Catalysts B Deuterium Kinetic Isotope Effects of Hydrocarbon Reactions Oxygen Isotopes ( 17 O , 18 O ) Miscellaneous Isotopes ( 15 N , 29 Si , 35 S ) Conclusions

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Location and orientation of adsorbed molecules in zeolites from solid-state REAPDOR NMR

Cited by 21 publications

References 28 publications

Investigating adsorption of organic compounds in metal-organic framework MIL-53

Investigating adsorption of organic compounds in metal-organic framework MIL-53

Inelastic neutron scattering of Na-zeolite A with in situ ammoniation: an examination of initial coordination

Isotopic Labeling and Kinetic Isotope Effects

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