Wells Stephen A, Cessford Naomi F, Seaton Nigel A, Düren Tina
Centre for Advanced Separations Engineering, Department of Chemical Engineering, University of Bath Bath UK
Institute for Materials and Processes, School of Engineering, University of Edinburgh Edinburgh UK.
RSC Adv. 2019 May 8;9(25):14382-14390. doi: 10.1039/c9ra01504c. eCollection 2019 May 7.
Metal-organic frameworks (MOF) comprising metal nodes bridged by organic linkers show great promise because of their guest-specific gas sorption, separation, drug-delivery, and catalytic properties. The selection of metal node, organic linker, and synthesis conditions in principle offers engineered control over both structure and function. For MOFs to realise their potential and to become more than just promising materials, a degree of predictability in the synthesis and a better understanding of the self-assembly or initial growth processes is of paramount importance. Using cobalt succinate, a MOF that exhibits a variety of phases depending on synthesis temperature and ligand to metal ratio, as proof of concept, we present a molecular Monte Carlo approach that allows us to simulate the early stage of MOF assembly. We introduce a new Contact Cluster Monte Carlo (CCMC) algorithm which uses a system of overlapping "virtual sites" to represent the coordination environment of the cobalt and both metal-metal and metal-ligand associations. Our simulations capture the experimentally observed synthesis phase distinction in cobalt succinate at 348 K. To the best of our knowledge this is the first case in which the formation of different MOF phases as a function of composition is captured by unbiased molecular simulations. The CCMC algorithm is equally applicable to any system in which short-range attractive interactions are a dominant feature, including hydrogen-bonding networks, metal-ligand coordination networks, or the assembly of particles with "sticky" patches, such as colloidal systems or the formation of protein complexes.
由有机连接体桥接金属节点构成的金属有机框架（MOF）因其特定客体的气体吸附、分离、药物递送及催化性能而展现出巨大潜力。原则上，金属节点、有机连接体及合成条件的选择可对结构和功能进行工程控制。为使MOF发挥其潜力并不仅仅成为有前景的材料，合成过程中的一定程度可预测性以及对自组装或初始生长过程的更好理解至关重要。以琥珀酸钴为例，它是一种根据合成温度和配体与金属比例呈现多种相的MOF，作为概念验证，我们提出一种分子蒙特卡罗方法，该方法使我们能够模拟MOF组装的早期阶段。我们引入一种新的接触簇蒙特卡罗（CCMC）算法，该算法使用重叠“虚拟位点”系统来表示钴的配位环境以及金属-金属和金属-配体缔合。我们的模拟捕捉到了在348 K下实验观察到的琥珀酸钴合成相区别。据我们所知，这是首次通过无偏分子模拟捕捉到不同MOF相作为组成函数的形成情况。CCMC算法同样适用于任何以短程吸引相互作用为主导特征的系统，包括氢键网络、金属-配体配位网络，或具有“粘性”斑块的粒子组装，如胶体系统或蛋白质复合物的形成。
