Force field simulation of guest induced gating phenomena

柔性可切换mof，特别是具有大量内自由度的柔性可切换mof的理论仿真一直是一个难点和未解决的问题。基于S1和S2合成的柱状层mof的完整第一性原理参数化MOF-FF模型，T2项目将进行分子动力学（MD）和大正则态MD （GCMD）模拟，以研究在热、压力或客体分子吸附的刺激下，这些体系在分子水平上的结构转变。与T1相比，重点更多地放在大长度和时间尺度上，但与T1有密切的相互作用，以便为电子结构计算提供结构信息，链接到光谱学项目P1和P2。在第一个资助期开发的热力学集成（TI） GCMD方法将得到扩展和验证，最终目标是使连接剂（QP1, QF1）具有功能化柔性侧链的fu- mof中小碳氢化合物的分离合理化。在用MD模拟筛选扩展连接体和/或客体分子库（S2）时，将确定确定可切换性的特定相互作用（QP4），另外作为T1 （QP1）的光谱性质的量子力学计算的输入。第一个资助期的有条不紊的成果将用于模拟大尺寸系统，允许研究不同相之间界面的形成和表面的影响（QP1&3）。主要目标是纳米颗粒的热开度（缺乏周期边界条件）和二维周期板的吸附开关（S1）。在尺寸上的进一步步骤将通过使用我们小组开发的粗粒度力场来研究更大尺寸范围内结构转变过程中的相关现象（QP3）。最后，新的GCMD方法将应用于模拟以短链醇为溶剂的液体吸附（在S2中研究），对于这种密集体系，标准GC蒙特卡罗方法是非常困难的（QP1, QF2）。

The theoretical simulation of flexible switchable MOFs, especially with a high number of inner degrees of freedom, is still a difficult and untackled problem. Based on the complete first-principles parameterized MOF-FF model for the pillared layer MOFs synthesized in S1 and S2, molecular dynamics (MD) and grand canonical MD (GCMD) simulations will be performed in project T2 to investigate the structural transformation of such systems on a molecular level, stimulated by heat, pressure or guest molecule adsorption. In contrast to T1, the focus is more on the large length and timescales, however, with a close interaction to T1 in order to provide structural information for the electronic structure calculations, linking to the spectroscopic projects P1 and P2. The thermodynamic integration (TI) GCMD approach developed in the first funding period will be extended and validated with the final target to rationalize the separation of small hydrocarbons in fu-MOFs with functionalized flexible side chains at the linker (QP1, QF1). In a screening of a library of extended linkers and/or guest molecules (S2) with MD simulations, specific interactions determining the switchability will be identified (QP4), additionally serving as input for quantum mechanics calculations of spectroscopic properties by T1 (QP1). The methodical achievements of the first funding period will be exploited to simulate large size systems, allowing to study the formation of interfaces between different phases and the impact of surfaces (QP1&3). Primary targets are the thermal opening of nanoparticles (absence of periodic boundary conditions) and the adsorptive switching of 2D-periodic slabs (S1). A further step in size will be achieved by using coarse grained force fields developed in our group to investigate correlated phenomena during the structural transformation on an even larger size range (QP3). Finally, the novel GCMD methods will be applied for the simulation of liquid adsorption with short chain alcohols as solvent (studied in S2), which is notoriously difficult for standard GC Monte Carlo methods for such dense systems (QP1, QF2).