Elucidating correlated defects in metal organic frameworks using theory-guided inelastic neutron scattering spectroscopy

Cavalcante, Lucas S. R.; Dettmann, Makena A.; Sours, Tyler; Yang, Dong; Daemen, Luke L.; Gates, Bruce C.; Kulkarni, Ambarish; Moulé, Adam J.

doi:10.1039/d2mh00914e

Cited by 5 publications

(4 citation statements)

References 58 publications

(89 reference statements)

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“…The low-frequency modes, in particular, will be more prone to anharmonic behavior. As the presence of defects can primarily be observed through fingerprints in the low-frequency spectrum, , the simulation of the corresponding phonon modes benefits from the dynamic approach. The experimental Raman spectrum of our UiO-66 sample does indeed feature a Raman band at 20 cm –1 (mode A in Figure ), which can, with the help of our simulations, be assigned to the presence of a cluster defect.…”

Section: Vibrational Properties Of Nanostructured Materialsmentioning

confidence: 99%

A Critical Assessment on Calculating Vibrational Spectra in Nanostructured Materials

Hoffman,

Temmerman,

Campbell

et al. 2023

J. Chem. Theory Comput.

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Vibrational spectroscopy is an omnipresent spectroscopic technique to characterize functional nanostructured materials such as zeolites, metal−organic frameworks (MOFs), and metal−halide perovskites (MHPs). The resulting experimental spectra are usually complex, with both low-frequency framework modes and high-frequency functional group vibrations. Therefore, theoretically calculated spectra are often an essential element to elucidate the vibrational fingerprint. In principle, there are two possible approaches to calculate vibrational spectra: (i) a static approach that approximates the potential energy surface (PES) as a set of independent harmonic oscillators and (ii) a dynamic approach that explicitly samples the PES around equilibrium by integrating Newton's equations of motions. The dynamic approach considers anharmonic and temperature effects and provides a more genuine representation of materials at true operating conditions; however, such simulations come at a substantially increased computational cost. This is certainly true when forces and energy evaluations are performed at the quantum mechanical level. Molecular dynamics (MD) techniques have become more established within the field of computational chemistry. Yet, for the prediction of infrared (IR) and Raman spectra of nanostructured materials, their usage has been less explored and remain restricted to some isolated successes. Therefore, it is currently not a priori clear which methodology should be used to accurately predict vibrational spectra for a given system. A comprehensive comparative study between various theoretical methods and experimental spectra for a broad set of nanostructured materials is so far lacking. To fill this gap, we herein present a concise overview on which methodology is suited to accurately predict vibrational spectra for a broad range of nanostructured materials and formulate a series of theoretical guidelines to this purpose. To this end, four different case studies are considered, each treating a particular material aspect, namely breathing in flexible MOFs, characterization of defects in the rigid MOF UiO-66, anharmonic vibrations in the metal−halide perovskite CsPbBr 3 , and guest adsorption on the pores of the zeolite H-SSZ-13. For all four materials, in their guest-and defect-free state and at sufficiently low temperatures, both the static and dynamic approach yield qualitatively similar spectra in agreement with experimental results. When the temperature is increased, the harmonic approximation starts to fail for CsPbBr 3 due to the presence of anharmonic phonon modes. Also, the spectroscopic fingerprints of defects and guest species are insufficiently well predicted by a simple harmonic model. Both phenomena flatten the potential energy surface (PES), which facilitates the transitions between metastable states, necessitating dynamic sampling. On the basis of the four case studies treated in this Review, we can propose the following theoretical guidelines to simulate accurate vibrational spectra of functional soli...

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Section: Vibrational Properties Of Nanostructured Materialsmentioning

confidence: 99%

A Critical Assessment on Calculating Vibrational Spectra in Nanostructured Materials

Hoffman,

Temmerman,

Campbell

et al. 2023

J. Chem. Theory Comput.

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“…Coupled with density functional theory (DFT) simulations, INS can quantitatively validate the assignment of different molecular configurations and molecular defects. 43,44 In addition, the combination of INS, DFT, and a dynamic delocalization transport model 10,45 has yielded a more accurate prediction of μ h than any other method 41 and even enables visualization of dynamic disorder for improved synthesis. 46 The BDT-H and BDT-F trimers studied here can assume several different polymorphs because of the two dihedral bonds and syn/syn, anti/anti, and anti/syn interactions with neighboring molecules.…”

Section: ■ Introductionmentioning

confidence: 99%

“…INS enables unprecedented accuracy in the measurement of phonon modes from 3 to 5000 meV. Coupled with density functional theory (DFT) simulations, INS can quantitatively validate the assignment of different molecular configurations and molecular defects. , In addition, the combination of INS, DFT, and a dynamic delocalization transport model , has yielded a more accurate prediction of μ h than any other method and even enables visualization of dynamic disorder for improved synthesis …”

Section: Introductionmentioning

confidence: 99%

Design Rules to Optimize the Intermolecular and Long-Range Packing of Organic Semiconductor Crystals

Maleki,

Thorley,

Iqbal

et al. 2024

Chem. Mater.

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Understanding the structure and configurations of small-molecule organic semiconductor (OSC) materials is essential in modifying their material properties. Here, we use density functional theory (DFT) to explore the impact of intramolecular noncovalent interactions on the isomerization and structure of the benzodithiophene (BDT) trimer. Fluorine substitutions modify the dihedral coupling between BDTs on the same molecule, thereby significantly increases charge mobility up to 13.2 cm 2 V −1 s −1 . In the fluorinated isomers, the formation of hydrogen bonds overcomes the repulsive S•••S interaction in the syn-conformer, leading to a more planar backbone structure. To validate the DFT simulations, we simulated inelastic neutron scattering (INS) spectroscopy of different anti-and syn-isomers in mixed configuration crystals and compared them to measured INS. Two main messages emerge from this study. (1) Although the through space interaction of fluorine with sulfur is the main contributor to dihedral planarization, H-bonding formed through selective fluorination plays a critical role. (2) A crystal structure that includes a mixture of several configurations could have significant mobility, while the dihedral disorder is mitigated by configurations that are energetically very similar. Our investigation reveals that both syn-and anti-conformers are common in the BDT-trimer crystal, demonstrating that isomeric or configuration purity is not a prerequisite for high charge mobility over 10 cm 2 V −1 s −1 . This work provides a fundamental understanding of the interplay between intramolecular interactions, isomerization, and side chain effects in OSC materials, guiding the design of new generations of OSC materials.

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“…In recent years, inelastic neutron scattering (INS) spectroscopy has emerged as a characterization technique for materials, mainly due to notable improvements in spectrometer sensitivity, e.g., LAGRANGE at ILL [22], TOSCA at ISIS [23], and VISION at Oak Ridge [24], which has made this spectroscopic technique more amenable to small quantities and more structured samples. Examples of the application of this spectroscopic technique across a wide range of different systems can be found in the literature [25][26][27][28][29][30][31]. In all cases, the interpretation of the experimental INS spectra takes advantage of the ease of generating INS spectra from quantum mechanical frequency calculations.…”

Section: Introductionmentioning

confidence: 99%

Intermolecular Interactions in 3-Aminopropyltrimethoxysilane, N-Methyl-3-aminopropyltrimethoxysilane and 3-Aminopropyltriethoxysilane: Insights from Computational Spectroscopy

Nolasco,

Parker,

Vaz

et al. 2023

IJMS

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In this work, a computational spectroscopy approach was used to provide a complete assignment of the inelastic neutron scattering spectra of three title alkoxysilane derivatives—3-aminopropyltrimethoxysilane (APTS), N-methyl-3-aminopropyltrimethoxysilane (MAPTS), and 3-aminopropyltriethoxysilane (APTES). The simulated spectra obtained from density functional theory (DFT) calculations exhibit a remarkable match with the experimental spectra. The description of the experimental band profiles improves as the number of molecules considered in the theoretical model increases, from monomers to trimers. This highlights the significance of incorporating non-covalent interactions, encompassing classical NH···N, N–H···O, as well as C–H···N and C–H···O hydrogen bond contacts, to achieve a comprehensive understanding of the system. A distinct scenario emerges when considering optical vibrational techniques, infrared and Raman spectroscopy. In these instances, the monomer model provides a reasonable description of the experimental spectra, and no substantial alterations are observed in the simulated spectra when employing dimer and trimer models. This observation underscores the distinctive ability of neutron spectroscopy in combination with DFT calculations in assessing the structure and dynamics of molecular materials.

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Elucidating correlated defects in metal organic frameworks using theory-guided inelastic neutron scattering spectroscopy

Abstract: Metal Organic Frameworks (MOFs) that incorporate metal oxide cluster nodes, exemplified by UiO-66, have been widely studied, especially in terms of their deviations from the ideal, defect-free crystalline structures. While...

Cited by 5 publications

References 58 publications

A Critical Assessment on Calculating Vibrational Spectra in Nanostructured Materials

A Critical Assessment on Calculating Vibrational Spectra in Nanostructured Materials

Design Rules to Optimize the Intermolecular and Long-Range Packing of Organic Semiconductor Crystals

Intermolecular Interactions in 3-Aminopropyltrimethoxysilane, N-Methyl-3-aminopropyltrimethoxysilane and 3-Aminopropyltriethoxysilane: Insights from Computational Spectroscopy

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