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Controlling gas mass transport in materials through phase transitions for enhanced gas storage
Redwine, Grace E. B.
Redwine, Grace E. B.
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2025
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Abstract
The transition to renewable energy requires efficient hydrogen storage and carbon dioxide recovery technologies to mitigate gas emissions and facilitate the adoption of clean energy sources. Hydrogen, a high-energy-density fuel, presents storage challenges due to its low volumetric density. Materials-based hydrogen storage, particularly through physisorption in metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), offers a promising alternative to conventional high-pressure or cryogenic storage methods. However, improving storage capacity, desorption control, and processability remains a challenge. Similarly, carbon recovery technologies must be optimized to reduce energy requirements while maintaining high CO2 sorption efficiency. This thesis explores novel materials-based strategies for gas storage and separation, with an emphasis on polymer mobility and phase transitions to control sorption and desorption processes.
This work begins with a review of polymer-encapsulated framework materials,
summarizing their synthesis, properties, and potential for gas storage applications (Chapter 2). Polymer encapsulation can improve the processability of porous frameworks while also influencing gas sorption behavior. In Chapter 3, polymer-framework composites are investigated for hydrogen storage, demonstrating that encapsulation introduces a temperature-dependent diffusion barrier. Below the polymer’s glass transition temperature (Tg), hydrogen desorption is inhibited, providing a tunable mechanism for controlled gas release.
To further understand the role of polymer mobility in hydrogen diffusion, Chapter 4 employs nuclear magnetic resonance (NMR) relaxometry to study polymer segmental motion. By modifying polymer structures, the study identifies key factors that influence hydrogen transport and retention. These findings suggest that polymer engineering can enhance the performance of physisorption-based hydrogen storage materials.
Chapter 5 shifts focus to CO2 capture, exploring ionic liquid crystals (ILCs) as sorbents. A unique phase transition-driven desorption mechanism is discovered, wherein CO2 release occurs over the melting point of the ILC. This behavior suggests that ILCs could offer a lower-energy alternative to conventional thermal swing regeneration processes.
Overall, this thesis advances the understanding of gas transport in polymer-modified materials, providing insights into the design of more efficient hydrogen storage and CO2 capture systems. By leveraging phase transitions and polymer dynamics, this work contributes to scalable, energy-efficient solutions for clean energy applications.
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