The ligand field in low-crystallinity metal-organic frameworks investigated by soft X-ray core-level absorption spectroscopy
The ligand field in low-crystallinity metal-organic frameworks investigated by soft X-ray core-level absorption spectroscopy
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软X射线核能级吸收光谱研究低结晶度金属有机骨架中的配体场
DOI：
10.1039/d2cp01415g
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发表时间：
2022
影响因子：
3.3
通讯作者：
Wadati Hiroki
中科院分区：
文献类型：
--
作者：
Yamagami Kohei;Yoshino Haruka;Yamagishi Hirona;Setoyama Hiroyuki;Tanaka Arata;Ohtani Ryo;Ohba Masaaki;Wadati Hiroki
过渡金属离子的配位场是实现新的物理化学性质机理的关键因素。然而，低结晶度状态，包括非晶态，排除了使用结晶学技术、紫外和红外光学方法和磁测量来澄清过渡金属离子的电子结构关系。在这里，我们证明了软X射线2p→3D芯级吸收光谱系统地揭示了低结晶度氰化物桥联金属有机骨架(MOF)M[Ni(CN)4](MNi；M=Mn，Fe，Co，Ni)和Ni[Pd(CN)4](NiPd)中氮配位过渡金属离子的局域3D电子态。在NiNi和NiPd中，具有正方平面对称性的N配位Ni离子表现出很强的轨道杂化和配体-金属电荷转移效应。在MnNi、FeNi和CoNi中，用多重态LF理论揭示了LF中晶态电场分裂与过渡金属-氮键长度之间的关系。不管不同的局域对称性，我们的结果表明，L2，3边XAS是获得关于过渡金属离子表征低结晶度MOF功能的元素特定知识的强大工具，并将成为吸引人的平台的基础，例如吸附/解吸材料。
The ligand field (LF) of transition metal ions is a crucial factor in realizing the mechanism of novel physical and chemical properties. However, the low-crystallinity state, including the amorphous state, precludes the clarification of the electronic structural relationship of transition metal ions using crystallographic techniques, ultraviolet and infrared optical methods, and magnetometry. Here, we demonstrate that soft X-ray 2p → 3d core-level absorption spectroscopy (L2,3-edge XAS) systematically revealed the local 3d electronic states, including in the LF, of nitrogen-coordinated transition-metal ions for low-crystallinity cyanide-bridged metal–organic frameworks (MOFs) M[Ni(CN)4] (MNi; M = Mn, Fe, Co, Ni) and Ni[Pd(CN)4] (NiPd). In NiNi and NiPd, N-coordinated Ni ions with square-planar symmetry exhibit strong orbital hybridization and ligand-to-metal charge transfer effects. In MnNi, FeNi, and CoNi, the correlation between the crystalline electric field splitting in the LF and the transition metal–nitrogen bonding length is revealed using the multiplet LF theory. Regardless of the different local symmetries, our results indicate that L2,3-edge XAS is a powerful tool for gaining element-specific knowledge about the transition–metal ion characterizing the functionality of low-crystallinity MOFs and will be the foundation for an attractive platform, such as adsorption/desorption materials.