In Situ High-Pressure Study of Metal-Organic Frameworks and Their Performance for CO2 Storage Probed by Vibrational Spectroscopy
Metal-organic frameworks (MOFs) are an important class of porous materials, owing to their potential applications in a variety of areas, including gas storage, molecular separations, catalysis, sensors and so on. Most importantly, their extraordinary surface areas, tunable pore properties and potential for industrial scale production have made MOFs a promising material for clean energy applications, such as CO2 storage. The chemical and mechanical stabilities of MOFs play a crucial role in their CO2 storage performance, which require extreme loading pressures that are far beyond ambient pressure at times. Application of high external pressure (e.g., in gigapascal range) on MOFs can significantly alter the framework structure, pore opening and consequently the adsorption properties. This Ph.D. work focuses on the investigation of high pressure effects on the structure and CO2 adsorptive performance of MOFs by in situ vibrational spectroscopy. Four types of MOFs with different topologies, structures and porosities have been studied under high pressures. We showed that all the MOFs exhibited high stabilities under extreme compression, retaining the chemical connectivity and porosity for CO2 storage. Strong guest-host interactions between CO2 and the frameworks as well as additional adsorption sites has been observed, indicating enhanced CO2 storage in the framework at high pressures. As guest molecules, CO2 has substantially enhanced the stability of MOFs and strongly influenced the pressure behavior of the frameworks. This work demonstrates great potential for MOF-based greenhouse gas storage applications.
Metal-organic frameworks, high pressure, diamond anvil cell, infra-red spectroscopy, Raman spectroscopy, CO2 storage
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