MOLECULAR DYNAMICS STUDIES ON THE INFLUENCE OF SOLVENT ON THE SELF-ASSEMBLY OF METAL-ORGANIC FRAMEWORKS

Abstract

Metal-organic frameworks (MOFs) are a promising class of functional porous materials. Their exceptional characteristics can be fine-tuned through the careful selection of building blocks and thorough design of synthesis conditions to customise MOFs with specific features for diverse applications. Optimization of synthesis conditions, such as the choice of solvent and thermal regime in solvothermal synthesis, is also crucial for the production scale-up and adoption of these materials for industrial applications. Achieving this requires an in-depth understanding of MOF self-assembly at the molecular level. This understanding is currently lacking. N, N-dimethylformamide (DMF) is the mostly used solvent in MOF-5 synthesis. Although it is an effective solvent due to its favourable solvent properties, it poses a negative environmental impact and health hazard due to its toxicity. In this study, we aimed to understand how the choice of solvents affects the self-assembly process. This could ultimately lead to a shift in synthetic approaches for MOFs towards using more environmentally friendly solvents. With this in mind, we considered five solvents - N, N-Diethyl-meta-toluamide (DEET), N, N-diethyl formamide (DEF), DMF, propylene carbonate (PRC) and tetrahydrofuran (THF) – medium for MOF-5 self-assembly using classical molecular dynamics. Previously, a similar approach was applied to explore the self-assembly of MOF-5 in DMF. The extension of this approach to other solvents is attempted in this thesis for the first time. The primary objectives here were to i) firstly, establish how accurately current molecular models can reproduce bulk liquid properties of solvents, such as density, under ambient conditions; and ii) secondly, to explore if the presence of different solvents leads to uniquely distinct scenarios of self-assembly. Indeed, our findings propose that the current molecular models provide a reasonable description of organic solvents. Importantly, we also observed different scenarios of self-assembly of MOF-5 in five solvents under consideration. In particular, lower molecular weight solvents tend to lead to structures that do resemble the initial formation of the reticular cage of MOF-5. While these studies are very preliminary, they highlight the utility of theoretical approaches such as classical molecular dynamics in understanding the temporal evolution of MOF self-assembly under various conditions.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Andrew Masters (Supervisor) & Lev Sarkisov (Supervisor)