三维共价有机框架的局部结构与动力学
Local Structure and Dynamics of Three-Dimensional Covalent Organic Frameworks
- University of California, Berkeley（加州大学伯克利分校）
- Dipartimento di Chimica, Università degli Studi di Roma La Sapienza（罗马大学化学系）
- Columbia University（哥伦比亚大学）
- Brookhaven National Laboratory（布鲁克海文国家实验室）
- University of California Santa Barbara（加州大学圣塔芭芭拉分校）
- Tsinghua University（清华大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究结合同步辐射X射线对分布函数分析与机器学习加速的分子动力学模拟，解析两种三维亚胺连接COFs的局部结构与动力学，明确其柔性/刚性调控机制，为COFs动态功能设计提供新方法。
AI中文摘要：
解析和控制共价有机框架（COFs）的局部动力学性质仍是核心挑战，尤其是当COFs由大尺寸、柔性构筑单元组装而成时。本研究将同步辐射X射线对分布函数（PDF）分析与机器学习加速的分子动力学（MD）模拟相结合，解析两种三维亚胺连接COFs的局部结构与动力学：COF-682{[(DHP)(TAM)]$_{亚胺}$}由6,13-二氢并五苯（DHP）和四(4-氨基苯基)甲烷（TAM）组装而成，COF-612{[(HBC-LA$_{12}$)(HAPT)$_2$]$_{亚胺}$}由纳米石墨烯十二苯甲醛六{[3,5-双($p$-甲酰基苯基)-4,6-二甲氧基苯基]}六苯并蔻（HBC-LA$_{12}$）和2,3,6,7,14,15-六(4-氨基苯基)三蝶烯（HAPT）组装而成。通过系综平均计算对实验PDF进行验证后，模拟结果显示：DHP连接基的暴露π表面与V形几何，通过面-面对面及偏移π堆积相互作用赋予COF-682更强的局部柔性，这两种相互作用的平均层间距与环平面倾斜角存在差异；相比之下，扩展的纳米石墨烯连接基通过维持其稠合核心的平面性使COF-612刚性化，而连接基的侧芳环则赋予两种COFs更强的 librational（ librational 保留）能力。模拟还进一步提供了连接基平移与取向运动的定量测量结果，揭示了如何通过平衡非共价相互作用与不同程度的芳香刚性来调控COFs的局部动力学。该PDF-MD实验-计算方法有望成为超越传统晶体学的通用方法，用于深入理解COFs的局部性质，从而指导其动态功能的设计。
英文摘要：
Resolving and controlling the local dynamical properties of covalent organic frameworks (COFs) remains a central challenge, particularly when assembled from large, flexible building units. Here, we combine synchrotron X-ray pair distribution function (PDF) analyses with machine learning-accelerated molecular dynamics (MD) simulations to resolve the local structure and dynamics of two three-dimensional imine-linked COFs, COF-682 {[(DHP)(TAM)]$_{imine}$}, assembled from 6,13-dihydropentacene (DHP) and tetrakis(4-aminophenyl)methane (TAM), and COF-612 {[(HBC-LA$_{12}$)(HAPT)$_2$]$_{imine}$}, assembled from nanographene dodecabenzaldehyde hexakis{[3,5-bis($p$-formylphenyl)-4,6-dimethoxyphenyl]}hexabenzocoronene (HBC-LA$_{12}$) and 2,3,6,7,14,15-hexa(4-aminophenyl)triptycene (HAPT). Validated against the experimental PDFs through ensemble-averaged calculations, the simulations show that the exposed $π$-surface and V-shaped geometry of the DHP linker endow COF-682 with enhanced local flexibility through face-to-face and offset $π$-stacking interactions differing in both their average interplanar separation and their ring-plane tilt angle. In contrast, the extended nanographene linker rigidifies COF-612 by maintaining the planarity of its fused cores, while the linker pendant aryl rings equip both COFs with enhanced librational ability. The simulations further provide quantitative measures of the translational and reorientational mobility of the linkers, revealing how local COF dynamics may be tuned by balancing non-covalent interactions and different degrees of aromatic rigidity. The PDF-MD experimental-computational approach holds promise as a general method beyond conventional crystallography to gain insights into the local properties of COFs with the aim of directing their dynamic function.
