Thermodynamic Insights into the Self-assembly of Zeolitic Imidazolate Frameworks from Computer Simulations

Abstract

New metal-organic frameworks (MOFs) are periodically synthesized all over the world due to the wide range of societally and environmentally relevant applications they possess. However, the mechanisms and thermodynamics associated to MOF self-assembly are poorly understood because of the difficulties in studying such a multi-scale process with molecular-level resolution. In this work, we performed well-tempered metadynamics simulations of the early nucleation and late growth steps of the self-assembly of ZIF-4 using a reactive force field. We found that the formation of building blocks is a complex, multi-step process that involves changes in the coordination of the metal ion. Saturating the ligand coordination of a metal ion is more energetically favorable during growth than during early nucleation. The addition of a fourth ligand is less exergonic than it is for the first three and the associated free energy is highly dependent on the local environment of the undercoordinated metal ion. The stability of this bond depends on the strength of the solvent--metal ion interaction. Incorporating a ligand to a ZIF-1 crystal is less favorable compared to the more stable ZIF-4 polymorph. Milder differences were found when comparing the growth of (100), (010) and (001) ZIF-4 surfaces.

37 pages, 10 figures, 4 tables

References in corpus (5)

• Well-Tempered Metadynamics: A Smoothly Converging and Tunable Free-Energy Method
• What makes zeolitic imidazolate frameworks hydrophobic or hydrophilic? The impact of geometry and functionalization on water adsorption
• Computer Simulation of the Early Stages of Self-Assembly and Thermal Decomposition of ZIF-8
• Microscopic Mechanism of the Thermal Amorphization of ZIF-4 and Melting of ZIF-zni Revealed via Molecular Dynamics and Machine Learning Techniques
• Phase Diagram of ZIF-4 Computed via Well-tempered Metadynamics

Cited by in corpus (3)

• 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