Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States.
Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States.
J Am Chem Soc. 2018 Jun 20;140(24):7411-7414. doi: 10.1021/jacs.8b03604. Epub 2018 Jun 6.
Partial oxidation of an iron-tetrazolate metal-organic framework (MOF) upon exposure to ambient atmosphere yields a mixed-valence material with single-crystal conductivities tunable over 5 orders of magnitude and exceeding 1 S/cm, the highest for a three-dimensionally connected MOF. Variable-temperature conductivity measurements reveal a small activation energy of 160 meV. Electronic spectroscopy indicates the population of midgap states upon air exposure and corroborates intervalence charge transfer between Fe and Fe centers. These findings are consistent with low-lying Fe defect states predicted by electronic band structure calculations and demonstrate that inducing metal-based mixed valency is a powerful strategy toward realizing high and systematically tunable electrical conductivity in MOFs.
在暴露于环境气氛下，铁四唑金属有机骨架（MOF）的部分氧化生成具有单晶电导率的混合价材料，其电导率可在 5 个数量级范围内调节，超过 1 S/cm，这是三维连接 MOF 的最高值。变温电导率测量表明，活化能较小，为 160 meV。电子光谱表明，空气暴露后存在中间隙态，并证实了 Fe 和 Fe 中心之间的价间电荷转移。这些发现与电子能带结构计算预测的低位 Fe 缺陷态一致，并证明了诱导金属基混合价是实现 MOF 中高且系统可调电导率的一种有力策略。
