Computer Simulation of the Early Stages of Self-Assembly and Thermal Decomposition of ZIF-8

Abstract

We employ all-atom well-tempered metadynamics simulations to study the mechanistic details of both the early stages of nucleation and crystal decomposition for the benchmark metal-organic framework ZIF-8. To do so, we developed and validated a force field that reliably models the modes of coordination bonds via a Morse potential functional form and employs cationic and anionic dummy atoms to capture coordination symmetry. We also explored a set of physically relevant collective variables and carefully selected an appropriate subset for our problem at hand. After a rapid increase of the Zn-N connectivity, we observe the evaporation of small clusters in favor of a few large clusters, that lead to the formation of an amorphous highly-connected aggregate. Zn(MIm)42- and Zn(MIm)3- complexes are observed, with lifetimes in the order of a few picoseconds, while larger structures, such as 4-, 5- and 6-membered rings, have substantially longer lifetimes of a few nanoseconds. The free ligands act as ``templating agents'' for the formation of the sodalite cages. ZIF-8 crystal decomposition results in the formation of a vitreous phase. Our findings contribute to a fundamental understanding of MOF's synthesis that paves the way to controlling synthesis products. Furthermore, our developed force field and methodology can be applied to model solution processes that require coordination bond reactivity for other ZIFs besides ZIF-8.

16 pages, 6 figures. This version corresponds to the accepted article, changes were applied in response to the peer-reviewing process. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in The Journal of Chemical Physics and may be found at https://aip.scitation.org/doi/10.1063/5.0128656

References in corpus (4)

• Well-Tempered Metadynamics: A Smoothly Converging and Tunable Free-Energy Method
• Accurate determination of crystal structures based on averaged local bond order parameters
• Collective Variables for the Study of Crystallization
• Computer Simulation of the Early Stages of Self-Assembly and Thermal Decomposition of ZIF-8

Cited by in corpus (8)

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• Coarse-grained dynamics of transiently-bound fast linkers
• Unveiling ZIF-8 nucleation mechanisms through molecular simulation: role of temperature, solvent and reactant concentration
• Systematic Study of Machine Learning Classification Algorithms of Zeolitic Imidazolate Framework Polymorphs
• Reactive Coarse Grained Force Field for Metal-Organic Frameworks applied to Modeling ZIF-8 Self-Assembly