Enhanced proton-transfer activity in imidazole@MIL-53(Al) systems revealed by molecular-dynamics simulations

Eisbein, Emanuel; Joswig, Jan‐Ole; Seifert, Gotthard

doi:10.1016/j.micromeso.2015.03.022

Cited by 12 publications

(8 citation statements)

References 40 publications

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“…Often, a hydrated polymer electrolyte membrane is utilized to serve as the proton-conducting material in a PEMFC, and thus, it introduces a serious limitation in the operating temperature range of the cell because of the boiling point of water. 5,6 In this regard, attempts have been made to develop waterfree electrolyte materials that exhibit facile proton transport, e.g., imidazole in both solid and liquid phases, 7−10 imidazole derivatives, 6,11,12 proton-conducting functionalized polymers, 13−24 etc. Recently, a long-range proton transport phenomenon was also observed in framework materials consisting of suitable proton donor/acceptor sites, even at very low water concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…In this regard, attempts have been made to develop water-free electrolyte materials that exhibit facile proton transport, e.g., imidazole in both solid and liquid phases, − imidazole derivatives, ,, proton-conducting functionalized polymers, − etc. Recently, a long-range proton transport phenomenon was also observed in framework materials consisting of suitable proton donor/acceptor sites, even at very low water concentrations. − Significant effort has also been focused on designing molecular crystals consisting of a hydrogen-bonded network that can act as water-free proton conductors .…”

Section: Introductionmentioning

confidence: 99%

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Proton Hopping Mechanisms in a Protic Organic Ionic Plastic Crystal

Mondal

Balasubramanian

2016

J. Phys. Chem. C

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We elucidate the dynamics and mechanism of proton transport in a protic organic ionic plastic crystal (POIPC) [TAZ][pfBu] by means of Born–Oppenheimer molecular dynamics simulations at 400 K and zero humidity. The arrangement of ionic species in the crystal offers a two-dimensional hydrogen bond network along which an acidic proton can travel from one cation to another through a sequence of molecular reorientations. The results suggest spontaneous autodissociation of the N–HN bond in the cation and multiple proton shuttle events from the cation’s nitrogen to the anion’s oxygen site in a native crystal. A complete proton transfer event is observed in simulations of a defective crystal with a single proton hole created in the cation. The barrier for proton transfer is determined using ab initio metadynamics simulations to be 7 kcal/mol, in agreement with experimental conductivity data. Using gas phase quantum chemical calculations, we propose [TAZ][CF3CF2CH2CF2SO3] as a compound that can show enhanced conductivity compared to that of [TAZ][pfBu].

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Proton Hopping Mechanisms in a Protic Organic Ionic Plastic Crystal

Mondal

Balasubramanian

2016

J. Phys. Chem. C

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“…Furthermore, Eisbein et al used molecular dynamics simulations to study the proton transfer in an imidazole loaded Al-MIL-53 structure. 29 They observed an ordering effect of the imidazole molecules through interactions with hydrophilic groups of the framework. This supports the finding of Bureekaew et al and suggested a general positive effect of hydrophobicity on the proton conductivity.…”

Section: Introductionmentioning

confidence: 99%

Structure property relationships affecting the proton conductivity in imidazole loaded Al-MOFs

et al. 2016

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The structures of the imidazole loaded derivatives of Al-MIL-53 [Al(OH)(1,4-BDC-(CH))] (x = 0, 1, 2) and CAU-11 ([Al(OH)(SDBA)]) (1,4-HBDC = terephthalic acid; HSDBA = 4,4'-sulfonyldibenzoic acid) were determined from powder X-ray diffraction data. Impedance spectroscopy measurements were carried out to evaluate their proton conductivities under anhydrous conditions at temperatures up to 110 °C. In Al-MIL-53-(CH)_HIm (x = 0, 1, 2) the formation of hydrogen bonds between the framework and the guest molecules results in a decrease in proton conductivity (x = 1.7 × 10, x = 1.9 × 10 and x = 1.7 × 10 S cm at 110 °C and E = 0.42, 0.41 and 0.46 eV, for 0, 1 and 2 CH-groups, respectively). The highest conductivity has been measured for CAU-11_HIm with 3.0 × 10 S cm at 110 °C (E = 0.19 eV), where no host-guest hydrogen bonding interactions are observed.

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“…This process has been extensively studied in bulk imidazole, 18−21 imidazole-based protic ionic liquids, 22,23 polymers, 24,25 and porous materials containing imidazole molecules. 10,26 In power generating devices, such as PEMFCs, the electrochemical reactions are controlled by the characteristics of the liquid/solid interface, or the electrolyte/electrode interface, and thus a detailed understanding of proton transportation in imidazole and imidazole-based protonconductive materials should include the proton solvation and diffusion behavior of the imidazolium cation in the interfacial region. The concerns are mainly of two aspects: (i) the proton propensity for the interface and (ii) the orientation of the imidazolium cation and imidazole molecules in the interfacial region.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Compared with water, the hydrogen bonds between imidazole molecules are relatively weak, and proton transportation can occur along consecutive hydrogen-bonded chains with the imidazole ring reorientation via Grotthuss mechanism. This process has been extensively studied in bulk imidazole, − imidazole-based protic ionic liquids, , polymers, , and porous materials containing imidazole molecules. , …”

Section: Introductionmentioning

confidence: 99%

Proton Propensity and Orientation of Imidazolium Cation at Liquid Imidazole–Vacuum Interface: A Molecular Dynamics Simulation

Yan

2020

J. Phys. Chem. B

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Imidazole has gained attention as an alternative to anhydrous proton conductor in high-temperature proton exchange membrane fuel cells. A detailed investigation of proton propensity and the orientation of the imidazolium cation at the liquid–vacuum interface is important for understanding the interfacial properties of imidazole-based proton-conductive materials. Here, we perform all-atom molecular dynamics simulation on a slab model of the liquid imidazole–vacuum interface. Proton transportation process between the imidazolium cation and neutral imidazole molecules is described by the multistate empirical valence bond model of imidazole developed previously. The imidazolium cation shows a tendency to stay in the bulk region rather than at the outermost surface, and the NN vectors and norm vectors of both the imidazolium cation and imidazole molecules are more probable to be perpendicular to the surface normal vector at the interface than in the bulk. The orientation of the hydrogen bond cluster shows the same tendency as the NN vectors, which indicates that proton transportation along the direction of the surface normal vector is hindered. The instantaneous surface analyses show that the fluctuation is depressed when the imidazolium cation is near the outermost surface, which makes it less favorable for the cation appearing at the interface.

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Enhanced proton-transfer activity in imidazole@MIL-53(Al) systems revealed by molecular-dynamics simulations

Cited by 12 publications

References 40 publications

Proton Hopping Mechanisms in a Protic Organic Ionic Plastic Crystal

Proton Hopping Mechanisms in a Protic Organic Ionic Plastic Crystal

Structure property relationships affecting the proton conductivity in imidazole loaded Al-MOFs

Proton Propensity and Orientation of Imidazolium Cation at Liquid Imidazole–Vacuum Interface: A Molecular Dynamics Simulation

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