Applied Physical Chemistry, Heidelberg University , 69120 Heidelberg, Germany.
ACS Nano. 2016 Jul 26;10(7):7085-93. doi: 10.1021/acsnano.6b03226. Epub 2016 Jul 6.
In the past, nanoporous metal-organic frameworks (MOFs) have been mostly studied for their huge potential with regard to gas storage and separation. More recently, the discovery that the electrical conductivity of a widely studied, highly insulating MOF, HKUST-1, improves dramatically when loaded with guest molecules has triggered a huge interest in the charge carrier transport properties of MOFs. The observed high conductivity, however, is difficult to reconcile with conventional transport mechanisms: neither simple hopping nor band transport models are consistent with the available experimental data. Here, we combine theoretical results and new experimental data to demonstrate that the observed conductivity can be explained by an extended hopping transport model including virtual hops through localized MOF states or molecular superexchange. Predictions of this model agree well with precise conductivity measurements, where experimental artifacts and the influence of defects are largely avoided by using well-defined samples and the Hg-drop junction approach.
在过去，纳米多孔金属-有机骨架（MOFs）主要因其在气体存储和分离方面的巨大潜力而被研究。最近，人们发现广泛研究的高度绝缘 MOF，HKUST-1，在负载客体分子时其电导率会显著提高，这引发了人们对 MOF 载流子输运性质的巨大兴趣。然而，观察到的高电导率很难与传统的输运机制相协调：简单的跳跃或能带输运模型都与可用的实验数据不一致。在这里，我们结合理论结果和新的实验数据，证明了观察到的电导率可以通过扩展的跳跃输运模型来解释，该模型包括通过局部 MOF 状态或分子超交换的虚拟跳跃。该模型的预测与精确的电导率测量结果吻合得很好，通过使用定义明确的样品和汞滴结接触法，避免了实验伪影和缺陷的影响。
