Thin Metal-Organic-Framework Membranes for High Pressure Carbon Dioxide Separation

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1160084LinMetal-organic-frameworks (MOF) represent a new group of microporous materials as membranes for gas and liquid separation applications. However, several fundamental issues unique for MOF membranes such as synthesis of thin MOF membranes and effects of adsorption induced structural change and thermal gradient on membrane separation properties have not been studied, and the unique separation properties of MOF membranes unattainable by traditional microporous inorganic membranes have not been explored for practical applications. This project is directed toward synthesis and characterization of thin, high flux microporous IRMOF-1 and ZIF-69 membranes and to study permeation and separation of these MOF membranes with a focus on understanding the effects of the adsorption induced structural change and thermal gradient on membrane transport properties. The study will explore the unique property of large pore MOF membranes, i.e., the carbon dioxide perm-selectivity increases with pressure for high pressure separation of carbon dioxide from natural gas. All existing membranes exhibit a decreasing perm-selectivity with increasing pressure. The work includes developing synthesis methods for preparation of thin (less than 5 ìm) large pore MOF membranes, identifying an adequate method for characterizing the quality of the MOF membranes, studying the permeation and separation properties of the MOF membranes at high pressures, and investigating adsorption induced structural change and thermal gradient on membrane characteristics. The membranes will be prepared by the secondary growth method with nano-sized MOF crystal seeds. A molecular probing method will be developed to examine the quality of the MOF membranes. Gas permeation of carbon dioxide, methane, nitrogen and hydrogen and separation properties of binary mixtures of these gases, particularly carbon dioxide/methane, for the IRMOF-1 and ZIF-69 membranes will be studied in a large pressure range (1-70 atm.) at 25-150C and compared with the results of modeling and molecular simulations. Structural changes and thermal gradient across the membranes during gas permeation will be studied and correlated to the gas permeation and separation properties of the membranes. The research conducted in this project will be transformational as it will address several major issues in synthesis, characterization and separation properties of membranes made from a new group of microporous materials. The results will be the basis for practical use of MOF membranes for separation of carbon dioxide from gas mixtures, in particularly natural gas, at high pressures. The fundamental work on synthesis and property study of IRMOF-1 and ZIF-69 membranes will expand inorganic membrane science which has so far been focused on metallic and metal oxide materials. The project will result in development of high performance membranes with good separation properties for gas mixtures containing CO2 at high pressures. One of the major applications of the membranes will be for natural gas purification to produce high pressure natural gas that is ready for transport in pipelines. The membranes will find other applications such as CO2 separation in pre-combustion carbon dioxide capture processes and will serve to increase industry's awareness of the many opportunities that exist for applying these new membranes. The combination of the unique properties of the MOF materials and thin film membrane technology represents a transformational approach to development of new membrane technologies for efficient separation of gas mixtures and will contribute to ensuring US competitiveness and technological lead in the area of CO2 capture. The project will also educate and train graduate and undergraduate students. In particular, female and minority students will be trained to become leaders in membrane science and separation technologies. An ASU graduate course in Inorganic Membranes and Membrane Separation Processes will incorporate the expanded perspectives resulting from the successful development of these MOF based gas separation devices. The project will also include the establishment of a laboratory demonstration unit using membranes for carbon dioxide separation for high school teachers and students as part of Arizona State University's "Science for Fun" outreach program.