First Principles Studies of The Metal-Organic Interface in Porous Frameworks
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Date
2022-10-26
Authors
Le, Khoa
Journal Title
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Publisher
University of Oregon
Abstract
Due to their generally poor conductivity, metal–organic frameworks (MOFs) have been limited in electrical applications. In this dissertation we explore structural deformation as a route to augmenting the electronic properties of these high surface area materials. We show that, under hydrostatic negative pressure, metallicity can be installed and we also elucidated the covalent characteristic of the metal-organic interface in 2D MOFs. Continuing our quest, we explore the deformation and phase change within 3D MOFs. Given the stability of metal-organic frameworks under numerous harsh conditions, bonding in MOFs has thought to be static. This project explores the metal-linker interface for a handful of carboxylate-based MOFs under various temperature conditions, which provides evident for dynamic bonding within these frameworks. Our insights to this phenomenon through the lens of density functional theory (DFT) combine with VT-DRIFT spectroscopy reveal specific vibrational modes coming from the carboxylate stretches that give rise to reversible metal-linker bonding within these materials. The metal-linker dynamics resemble the ubiquitous soft modes that trigger important phase transitions offering insights to several important events such as catalysis, negative thermal expansion, post-synthetic exchange that occurred in these frameworks. We applied the same methods onto Fe-based porous frameworks and elucidated Fe metal centers possess properties such as spin-crossover transition, mixed-valency, and cooperativity which together enhance the material's transport properties. With these knowledges, we proposed a design principle of retroffitting 2D Fe-based MOFs into 3D analog to achieve highly conductive MOFs. This study contributes a fundamentally new perspective for the design of next-generation conductive metal–organic materials.
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Keywords
Band Structure, Computational, Conductivity, DFT, Dynamic Bonding, Metal-Organic Frameworks