Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pune, 411 008, India.
Department of Physics, National Institute of Technology Karnataka, Surathkal, Mangalore, 575 025, India.
Nat Commun. 2022 Dec 12;13(1):7665. doi: 10.1038/s41467-022-35429-5.
Downsizing materials into hetero-structured thin film configurations is an important avenue to capture various interfacial phenomena. Metallic conduction at the interfaces of insulating transition metal oxides and organic molecules are notable examples, though, it remained elusive in the domain of coordination polymers including metal-organic frameworks (MOFs). MOFs are comprised of metal centers connected to organic linkers with an extended coordination geometry and potential void space. Poor orbitals overlap often makes these crystalline solids electrical insulators. Herein, we have fabricated hetero-structured thin film of a Mott and a band insulating MOFs via layer-by-layer method. Electrical transport measurements across the thin film evidenced an interfacial metallic conduction. The origin of such an unusual observation was understood by the first-principles density functional theory calculations; specifically, Bader charge analysis revealed significant accumulation and percolation of charge across the interface. We anticipate similar interfacial effects in other rationally designed hetero-structured thin films of MOFs.
将材料缩小到异质结构的薄膜配置是捕捉各种界面现象的重要途径。绝缘过渡金属氧化物和有机分子界面的金属传导就是一个显著的例子，尽管在包括金属有机骨架（MOFs）在内的配位聚合物领域，这种现象仍然难以捉摸。MOFs 由金属中心与有机连接体组成，具有扩展的配位几何形状和潜在的空隙空间。较差的轨道重叠通常使这些晶体固体成为电绝缘体。在此，我们通过逐层法制备了莫特和能带绝缘 MOFs 的异质结构薄膜。薄膜的电输运测量证明了界面处的金属传导。这种异常观察的起源可以通过第一性原理密度泛函理论计算来理解；具体来说，Bader 电荷分析表明，电荷在界面上有明显的积累和渗流。我们预计在其他合理设计的 MOFs 异质结构薄膜中也会出现类似的界面效应。
