Band gap opening from displacive instabilities in layered covalent-organic frameworks
Band gap opening from displacive instabilities in layered covalent-organic frameworks
复制标题
层状共价有机框架中的位移不稳定性导致带隙打开
DOI：
10.1039/d2ta02993f
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发表时间：
2022
影响因子：
11.9
通讯作者：
Huang J
中科院分区：
文献类型：
--
作者：
Huang J
共价有机框架（COF）提供高度的化学和结构灵活性。有一个大家族的COF建立从二维片堆叠形成扩展晶体。虽然通常将堆叠表示为与一个重复层（“AA”）重叠，但越来越多的证据表明可以获得更多样化的堆叠序列。在这里，我们报告了一个计算研究，使用密度泛函理论的层堆叠在两个原型COFs，TP-Azo和DAAQ-TFP，这已显示出高性能的锂离子电池电极。我们发现了一个惊人的偏好滑移结构层之间的水平偏移范围从1.7毫米到3.5毫米的势能最小值，形成一个低能量环。相关的对称性破缺导致了底层电子结构的显著变化。发现0.8-1.4 eV的带隙开口是由于下面的价带和导带色散的修改，如从π轨道重叠的变化所解释的。讨论了COF的筛选和选择对能源应用的影响。
Covalent organic frameworks (COFs) offer a high degree of chemical and structural flexibility. There is a large family of COFs built from 2D sheets that are stacked to form extended crystals. While it has been common to represent the stacking as eclipsed with one repeating layer (“AA”), there is growing evidence that a more diverse range of stacking sequences is accessible. Herein, we report a computational study using density functional theory of layer stacking in two prototypical COFs, Tp-Azo and DAAQ-TFP, which have shown high performance as Li-ion battery electrodes. We find a striking preference for slipped structures with horizontal offsets between layers ranging from 1.7 Å to 3.5 Å in a potential energy minimum that forms a low energy ring. The associated symmetry breaking results in a pronounced change in the underlying electronic structure. A band gap opening of 0.8–1.4 eV is found due to modifications of the underlying valence and conduction band dispersion as explained from changes in the π orbital overlap. The implications for the screening and selection of COF for energy applications are discussed.