Development of novel hydroxide ion conductors using post synthetic method

我们展示了一种金属-有机骨架(MOF)设计用于氢氧化物离子的包合。采用盐包合法将烷基氢氧化铵作为离子载体引入碱稳定的ZIF-8分子筛(ZIF：沸石咪唑骨架)中。我们发现，四丁基铵盐通过盐的烷基和骨架之间的疏水作用被固定在孔内，这显著增加了ZIF-8的亲水性。此外，包括盐在内的ZIF-8表现出了OH-离子交换能力，这意味着MOF中存在可自由交换的OH-离子。含OH-离子的ZIF-8在25℃时的离子电导率为2.3×10-8 S cm-1，比空白的ZIF-8高出4个数量级。这是第一个基于MOF的氢氧化物离子导体的例子。

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 the ZIF-8. Furthermore, the ZIF-8 including the salt exhibited a capacity for OH- ion exchange, implying that freely exchangeable OH- ions are present in the MOF. The ZIF-8 containing OH- ions showed an ionic conductivity of 2.3 x 10-8 S cm-1 at 25 C, which is four orders of magnitude higher than that of the blank ZIF-8. This is the first example of an MOF-based hydroxide ion conductor.