Theory of Borazine-Derived Nanothreads: Enumeration, Reaction Pathways, and Piezoelectricity
Theory of Borazine-Derived Nanothreads: Enumeration, Reaction Pathways, and Piezoelectricity
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环硼嗪衍生的纳米线理论：计数、反应途径和压电
DOI：
10.1021/acsnano.2c02778
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发表时间：
2022
期刊：
影响因子：
17.1
通讯作者：
Crespi, Vincent H.
中科院分区：
文献类型：
--
作者：
Wang, Tao;Xu, En-Shi;Chen, Bo;Hoffmann, Roald;Crespi, Vincent H.
纳米线是通过压力诱导聚合沿着堆叠的多重不饱和（或高度应变）分子（例如苯（或立方烷））形成的一维大分子。环硼氮烷与苯是等电子的，但具有显著的键极性，因此激发了对具有2、4和6的饱和度（定义为每个环硼氮烷式单元的四配位硼和氮原子的数量）的环硼氮烷衍生的纳米线的理论检验。能量在从分子环硼氮烷到2度环硼氮烷衍生的线时增加，然后随着形成更多的σ键而对于4度和6度纳米线降低。在骨架的键合拓扑的重复单元内不超过两个环硼氮烷式单元的限制下，仅存在13个完全饱和的（即，6度）硼氮烷衍生的纳米线，其避免了能量昂贵的同极键（与苯衍生的线的50多个这样的候选物相比）。其中只有两种比环硼氮烷更稳定。从分子环硼氮烷到这两个度-6环硼氮烷衍生的纳米线的假设途径进行了讨论。这种相对缺乏的结果可能有助于反应产物的动力学控制。除了对碳基线预测的高机械强度之外，诸如压电性和挠曲电性等特性可能可以访问硼氮衍生纳米线的极性晶格，在这些极薄但刚性的物体中具有有趣的表达前景。
Nanothreads are one-dimensional macromolecules formed by pressure-induced polymerization along stacks of multiply unsaturated (or highly strained) molecules such as benzene (or cubane). Borazine is isoelectronic to benzene yet with substantial bond polarity, thus motivating a theoretical examination of borazine-derived nanothreads with degrees of saturation of 2, 4, and 6 (defined as the number of four-coordinated boron and nitrogen atoms per borazine formula unit). The energy increases upon going from molecular borazine to degree-2 borazine-derived threads and then decreases for degree-4 and degree-6 nanothreads as more σ bonds are formed. With the constraint of no more than two borazine formula units within the repeat unit of the framework’s bonding topology, there are only 13 fully saturated (i.e., degree-6) borazine-derived nanothreads that avoid energetically costly homopolar bonds (as compared to more than 50 such candidates for benzene-derived threads). Only two of these are more stable than borazine. Hypothetical pathways from molecular borazine to these two degree-6 borazine-derived nanothreads are discussed. This relative paucity of outcomes may assist in kinetic control of reaction products. Beyond the high mechanical strength also predicted for carbon-based threads, properties such as piezoelectricity and flexoelectricity may be accessible to the polar lattice of borazine-derived nanothreads, with intriguing prospects for expression in these extremely thin yet rigid objects.