title: Design and synthesis of hydroxide ion-conductive metal-organic frameworks based on salt inclusion.
abstract: We demonstrate a metal-organic framework (MOF) design for the inclusion of hydroxide ions. Salt inclusion method was applied to an alkaline-stable ZIF-8 (ZIF = zeolitic imidazolate framework) to introduce alkylammonium hydroxides as ionic carriers. We found that tetrabutylammonium salts are immobilized inside the pores by a hydrophobic interaction between the alkyl groups of the salt and the framework, which significantly increases the hydrophilicity of ZIF-8. Furthermore, ZIF-8 including the salt exhibited a capacity for OH(-) ion exchange, implying that freely exchangeable OH(-) ions are present in the MOF. ZIF-8 containing OH(-) ions showed an ionic conductivity of 2.3 × 10(-8) S cm(-1) at 25 °C, which is 4 orders of magnitude higher than that of the blank ZIF-8. This is the first example of an MOF-based hydroxide ion conductor.
authors.affiliation: International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University , 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sadakiyo
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Kasai
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kato
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
authors.forename: Miho
authors.initials: M
authors.lastname: Yamauchi