CAREER: A new class of modified mesoporous silica membranes with controlled pore size and surface functionalization through unique synthetic approaches

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Abstract: Artificial membranes made from sand-like materials known as silica are potentially more energy efficient than other separation processes such as distillation (change in phase from liquid to gas) because there is no phase change required to perform the separation. In addition, the opportunity exists for combining reaction and separation within a single unit using membrane reactors, thereby increasing yield on thermodynamically-limited reactions. However, the fabrication of high-quality silica membranes with pore size control and surface chemistry control remains challenging because of the inherent limits of existing synthetic approaches used to fabricate silica membranes. The researchers at the University of Maine have achieved promising preliminary results on pore size control and surface chemistry control using new synthetic approaches toward fabricating silica membranes. These techniques are based on highly controlled catalyzed surface chemistry reactions that are used to modify mesoporous silica membranes. The reactions are atomically controlled at the surface to provide a self-limited pore size reduction and the functionalization of the mesoporous matrix. In this CAREER plan, the university of Maine will use the new synthesis technique, known as catalyzed-atomic layer deposition, to prepare silica membranes with controlled pore sizes in the pore size range of 10-20 angstroms and create new hybrid organic/inorganic membranes. This will be achieved using both vapor phase deposition and supercritical fluid CO2 deposition techniques. This will provide a new class of silica materials that may find application in the separations of higher molecular weight compounds as well as a new class of hybrid organic/inorganic silica-based membranes for gas/vapor separations. The research will focus upon understanding chemical, microstructural, permeation, and separation properties of the new materials while quantitatively linking the synthesis procedure to material performance. The proposed synthesis techniques offer a level of atomic control during the materials preparation that is not known today. The applications for these membranes are diverse and include separations of heavy distillates in petroleum processing, separations of organic compounds from lighter gases, separators for lithium-ion batteries, and bio-separations. These new synthetic techniques are expected to spur application towards different classes of materials, including adsorbents or even different inorganic membranes. The proposed education activities will affect all chemical engineering undergraduates at the University of Maine and a significant number of high school students, including those in some of Maines poorest and most geographically remote communities.