Mohamed Saad Aldin, Jiang Jianwen
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576.
Nano Lett. 2024 Oct 23;24(42):13431-13437. doi: 10.1021/acs.nanolett.4c04187. Epub 2024 Oct 8.
Many metal-organic frameworks (MOFs) undergo structural collapse upon solvent evacuation during activation, which is attributed to the capillary force generated by the solvent. However, little effort has been devoted to unveiling the nature of such a force. Herein, we employ molecular dynamics (MD) simulations to investigate the evacuation of different solvents in two MOFs (MOF-5 and UMCM-9). The contractive stress induced by solvent evacuation is quantified and unraveled to positively correlate with the surface tension of the solvent. Moreover, the mechanical strength (or amorphization) of the MOF is calculated using reactive MD simulations. By comparing the contractive stress with the amorphization stress, for the first time, we predict the likelihood of collapse of MOFs during activation by different solvents, which agrees well with the experiments. The methodology developed provides nanoscopic insights into the activation process; it can assist in avoiding structural collapse by judiciously selecting a proper solvent for activation or by modifying a framework.
许多金属有机框架材料（MOF）在活化过程中溶剂抽空时会发生结构坍塌，这归因于溶剂产生的毛细作用力。然而，对于揭示这种力的本质却鲜有研究。在此，我们采用分子动力学（MD）模拟来研究两种MOF（MOF-5和UMCM-9）中不同溶剂的抽空过程。对溶剂抽空引起的收缩应力进行了量化和解析，发现其与溶剂的表面张力呈正相关。此外，使用反应性MD模拟计算了MOF的机械强度（或非晶化）。通过比较收缩应力和非晶化应力，我们首次预测了不同溶剂在活化过程中MOF发生坍塌的可能性，这与实验结果吻合良好。所开发的方法为活化过程提供了纳米尺度的见解；它可以通过明智地选择合适的活化溶剂或对框架进行改性来帮助避免结构坍塌。
