Proton dynamics of two-dimensional oxalate-bridged coordination polymers

Satoshi Miyatsu, Maiko Kofu, Atsushi Nagoe, Takeshi Yamada, Masaaki Sadakiyo, Teppei Yamada, Hiroshi Kitagawa, Madhusudan Tyagi, Victoria García Sakai, Osamu Yamamuro

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Abstract

A two-dimensional porous coordination polymer (NH4)2(HOOC(CH2)4COOH)[Zn2(C2O4)3] (abbreviated as (NH4)2(adp)[Zn2(ox)3] (adp = adipic acid, ox = oxalate)), which accommodates water molecules between the [Zn2(ox)3] layers, is highly remarked as a new type of crystalline proton conductor. In order to investigate its phase behavior and the proton conducting mechanism, we have performed adiabatic calorimetry, neutron diffraction, and quasi-elastic neutron scattering experiments on a fully hydrated sample (NH4)2(adp)[Zn2(ox)3]·3H2O with the highest proton conductivity (8 × 10-3 S cm-1, 25 °C, 98% RH). Its isostructural derivative K2(adp)[Zn2(ox)3]·3H2O was also measured to investigate the role of ammonium ions. (NH4)2(adp)[Zn2(ox)3]·3H2O and K2(adp)[Zn2(ox)3]·3H2O exhibit higher order transitions at 86 K and 138 K, respectively. From the magnitude of the transition entropy, the former is of an order-disorder type while the latter is of a displacive type. (NH4)2(adp)[Zn2(ox)3]·3H2O has four Debye-type relaxations and K2(adp)[Zn2(ox)3]·3H2O has two similar relaxations above each transition temperature. The two relaxations of (NH4)2(adp)[Zn2(ox)3]·3H2O with very small activation energies (ΔEa < 5 kJ mol-1) are due to the rotational motions of ammonium ions and play important roles in the proton conduction mechanism. It was also found that the protons in (NH4)2(adp)[Zn2(ox)3]·3H2O are carried through a Grotthuss mechanism. We present a discussion on the proton conducting mechanism based on the present structural and dynamical information.

Original languageEnglish
Pages (from-to)17295-17304
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number32
DOIs
Publication statusPublished - Jul 23 2014

Fingerprint

Oxalates
oxalates
coordination polymers
Protons
Polymers
protons
Ammonium Compounds
conduction
Ions
Proton conductivity
Elastic scattering
Order disorder transitions
Calorimetry
Phase behavior
Neutron diffraction
Neutron scattering
Entropy
Activation energy
neutron diffraction
ions

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Miyatsu, S., Kofu, M., Nagoe, A., Yamada, T., Sadakiyo, M., Yamada, T., ... Yamamuro, O. (2014). Proton dynamics of two-dimensional oxalate-bridged coordination polymers. Physical Chemistry Chemical Physics, 16(32), 17295-17304. https://doi.org/10.1039/c4cp01432d

Proton dynamics of two-dimensional oxalate-bridged coordination polymers. / Miyatsu, Satoshi; Kofu, Maiko; Nagoe, Atsushi; Yamada, Takeshi; Sadakiyo, Masaaki; Yamada, Teppei; Kitagawa, Hiroshi; Tyagi, Madhusudan; García Sakai, Victoria; Yamamuro, Osamu.

In: Physical Chemistry Chemical Physics, Vol. 16, No. 32, 23.07.2014, p. 17295-17304.

Research output: Contribution to journalArticle

Miyatsu, S, Kofu, M, Nagoe, A, Yamada, T, Sadakiyo, M, Yamada, T, Kitagawa, H, Tyagi, M, García Sakai, V & Yamamuro, O 2014, 'Proton dynamics of two-dimensional oxalate-bridged coordination polymers', Physical Chemistry Chemical Physics, vol. 16, no. 32, pp. 17295-17304. https://doi.org/10.1039/c4cp01432d
Miyatsu, Satoshi ; Kofu, Maiko ; Nagoe, Atsushi ; Yamada, Takeshi ; Sadakiyo, Masaaki ; Yamada, Teppei ; Kitagawa, Hiroshi ; Tyagi, Madhusudan ; García Sakai, Victoria ; Yamamuro, Osamu. / Proton dynamics of two-dimensional oxalate-bridged coordination polymers. In: Physical Chemistry Chemical Physics. 2014 ; Vol. 16, No. 32. pp. 17295-17304.
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AU - Yamada, Teppei

AU - Kitagawa, Hiroshi

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