Proton conduction via lattice water molecules in oxalato-bridged lanthanide porous coordination polymers.
The proton conducting properties of two different structural types of porous coordination polymers [La2(ox)3(H2O)6]·4H2O (1) and [Er2(ox)3(H2O)6]·12H2O (2), where ox2-= oxalate, were investigated. 1 has a two-dimensional layered structure, whereas 2 has a three-dimensional structure. Both 1 and 2 have hydrophilic one-dimensional channels filled by lattice water molecules with hydrogen-bonding networks. The coordinated H2O molecules are Lewis acidic due to the lanthanoid ions donating protons to lattice-filling H2O molecules, thereby forming efficient proton conduction pathways. Alternating-current impedance analyses of 1 and 2 indicated significant proton conduction (σ = 3.35 × 10-7S cm-1at 368 K for 1, 1.79 × 10-6S cm-1at 363 K for 2 under RH = 100%, with Ea= 0.35 eV for 1 and 0.47 eV for 2), which was attributed to the Grotthuss mechanism via the lattice H2O molecules.
Department of Chemistry, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan. ryutaishikawa@fukuoka-u.ac.jp.
Ryuta
R
Ishikawa
Shunya
S
Ueno
Sadahiro
S
Yagishita
Hitoshi
H
Kumagai
Brian K
BK
Breedlove
Satoshi
S
Kawata