Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

Hoffmann, Herbert C.; Debowski, Marta; Müller, Philipp; Paasch, Silvia; Senkovska, Irena; Kaskel, Stefan; Brunner, Eike

doi:10.3390/ma5122537

Cited by 142 publications

(192 citation statements)

References 223 publications

(336 reference statements)

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“…While many of these techniques directly probe small-molecule dynamics related to rotations, vibrations, and diffusion, the resulting spectra can also be used to extract binding confi gurations, binding enthalpies, and even loading levels. While we do not intend to review all of these techniques individually, as they have been thoroughly covered elsewhere, [ 104,[109][110][111][112][113] we would like to point out that there are limitations related to data interpretation that can be signifi cantly aided by theoretical investigations. [ 114 ] Information pertaining to small-molecule interactions is often extracted from line shifts, widths, and/ or intensities.…”

Section: Experimental Approaches Limitations and The Need For Theorymentioning

confidence: 99%

Understanding Small‐Molecule Interactions in Metal–Organic Frameworks: Coupling Experiment with Theory

et al. 2015

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are intensive scientifi c efforts focused on the development of new physical adsorbents that might enable more energetically favorable gas separation, relative to traditional distillation or absorption processes. This feat is not easy, as the differences in the molecules of interest, such as CO 2 and N 2 -the main components in a postcombustion fl ue gas, are minimal. [ 2,3 ] As such, these separations require tailor-made adsorbent materials with molecule-specifi c chemical interactions on their internal surface. [ 4,5 ] Metal-organic frameworks (MOFs) are a particularly attractive class of porous adsorbents that are under intense investigation for gas separation due to their unmatched structural versatility. Many stable, 3D frameworks that offer unprecedented internal surface areas and the selective adsorption of a wide range of small guest molecules have been discovered. [ 6 ] The molecular nature of the organic ligand in an MOF provides a convenient modular approach to their synthesis and facile chemical tunability, creating a surge towards the directed design of new materials ( Figure 1 ). [7][8][9] Through judicious selection of the ligand and metal, which control pore size/shape and MOF-adsorbate interactions, MOF uptake properties, Metal-organic frameworks (MOFs) have gained much attention as nextgeneration porous media for various applications, especially gas separation/ storage, and catalysis. New MOFs are regularly reported; however, to develop better materials in a timely manner for specifi c applications, the interactions between guest molecules and the internal surface of the framework must fi rst be understood. A combined experimental and theoretical approach is presented, which proves essential for the elucidation of small-molecule interactions in a model MOF system known as M 2 (dobdc) (dobdc 4− = 2,5-dioxido-1,4-benzenedicarboxylate; M = Mg, Mn, Fe, Co, Ni, Cu, or Zn), a material whose adsorption properties can be readily tuned via chemical substitution. It is additionally shown that the study of extensive families like this one can provide a platform to test the effi cacy and accuracy of developing computational methodologies in slightly varying chemical environments, a task that is necessary for their evolution into viable, robust tools for screening large numbers of materials.

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Section: Experimental Approaches Limitations and The Need For Theorymentioning

confidence: 99%

Understanding Small‐Molecule Interactions in Metal–Organic Frameworks: Coupling Experiment with Theory

et al. 2015

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“…[1] Spectroscopic techniques, such as IR [2] and solid state NMR [3] are often used for probing these interactions. Crystallographic studies, both X-ray and neutron, utilizing various environmental cells have proven invaluable in determining the nature of host-guest interactions within MOFs and their guest-driven structural flexibility.…”

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confidence: 99%

Locating Gases in Porous Materials: Cryogenic Loading of Fuel‐Related Gases Into a Sc‐based Metal–Organic Framework under Extreme Pressures

et al. 2015

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An alternative approach to loading metal organic frameworks with gas molecules at high (kbar) pressures is reported. The technique, which uses liquefied gases as pressure transmitting media within a diamond anvil cell along with a single-crystal of a porous metal organic framework, is demonstrated to have considerable advantages over other gas-loading methods when investigating host-guest interactions. Specifically, loading the metal organic framework Sc2BDC3 with liquefied CO2 at 2 kbar reveals the presence of three adsorption sites, one previously unreported, and resolves previous inconsistencies between structural data and adsorption isotherms. A further study with supercritical CH4 at 3 -25 kbar demonstrates hyperfilling of the Sc2BDC3 and two high pressure displacive and reversible phase transitions are induced as the filled MOF adapts to reduce the volume of the system.Understanding how guest molecules in metal-organic framework (MOFs) interact with each other and the framework they occupy upon adsorption is vital for the development and commercial application of MOFs, for example in carbon capture and gas sequestration technologies. [1] Spectroscopic techniques, such as IR [2] and solid state NMR [3] are often used for probing these interactions. Crystallographic studies, both X-ray and neutron, utilizing various environmental cells have proven invaluable in determining the nature of host-guest interactions within MOFs and their guest-driven structural flexibility. [4] This is particularly important in the many cases where the uptake behavior, which can include conformational changes in the framework itself, can be perturbed by the type and amount of guest adsorbed. [5] One of the main reasons why so little data is available is that the experimental location of gas molecules in MOFs is challenging. The gas molecules are often disordered and exhibit thermal motion which is difficult to model crystallographically even when cooled close to the freezing temperature of the gas adsorbed. In-situ cells have been developed for collecting crystallographic data whilst exposing a MOF to a gaseous environment at tens, or even hundreds of bars of pressure in an effort to saturate the pores with gas molecules, though even here, the gas molecules are often difficult to observe experimentally. For these reasons, despite the intensive research in carbon capture technologies, relatively few crystallographic studies have been reported where CO2 molecules have been unambiguously located within MOFs. [6] The use of condensed gases as pressure transmitting media (PTM) in diamond anvil cells is commonplace in the fields of condensed matter physics and high-pressure mineralogy due to their excellent hydrostatic properties at very high-pressures (> 10 GPa) relative to common liquid PTMs. [7] He, Ar and Ne are typically used because they are chemically inert, whilst other gases have been studied for their diverse structural behavior. High temperature and pressure phases of CO2 and CH4 are of interest for understandin...

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“…In a second step, the natural abundance 15 N NMR spectra of grafted In-MIL-68-NH-Pro and In-MIL-68-NH-Gly-Pro were collected by DNP SENS. The low detection limit provided by the DNP NMR technique 40 makes it well suited to study host-guest type interactions in solids, 41 including post-synthetically functionalized MOFs. 42 DFT-calculated 15 N chemical shifts of selected MIL-68-NH-Pro and MIL-68-NH-Gly-Pro models were compared with 15 N NMR signals obtained from the DNP SENS experiments.…”

Section: Introductionmentioning

confidence: 99%

Molecular Level Characterization of the Structure and Interactions in Peptide‐Functionalized Metal–Organic Frameworks

Todorova

Rozanska

Gervais

et al. 2016

Chemistry A European J

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We use DFT, newly parameterized Molecular Dynamics simulations and last generation 15 N DNP surface enhanced solid-state NMR spectroscopy to understand graft-host interactions and effects imposed by the MOF host on peptide conformations in a peptide-functionalized MOF. Focusing on two grafts typified by MIL-68-Proline (-Pro) and MIL-68-Glycine-Proline (-Gly-Pro), we identified the most likely peptide conformations adopted in the functionalized hybrid frameworks. We found that hydrogen bond interactions between the graft and the surface hydroxyl groups of the MOF are key in determining the peptides conformation(s).15 N DNP SENS methodology shows unprecedented signal enhancements when applied to these peptide-functionalized MOFs. The calculated chemical shifts of selected MIL-68-NH-Pro and MIL-68-NH-Gly-Pro conformations are in a good agreement with the experimentally obtained 15 N NMR signals. The study shows that the conformations of peptides when grafted in a MOF host are unlikely to be freely distributed, and conformational selection is directed by strong host-guest interactions.

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Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

Cited by 142 publications

References 223 publications

Understanding Small‐Molecule Interactions in Metal–Organic Frameworks: Coupling Experiment with Theory

Understanding Small‐Molecule Interactions in Metal–Organic Frameworks: Coupling Experiment with Theory

Locating Gases in Porous Materials: Cryogenic Loading of Fuel‐Related Gases Into a Sc‐based Metal–Organic Framework under Extreme Pressures

Molecular Level Characterization of the Structure and Interactions in Peptide‐Functionalized Metal–Organic Frameworks

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