CAREER: Molecular Layer Deposition of Porous Organic Frameworks

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

The technological advances made to control the synthesis and growth of materials have been the cornerstone of many scientific discoveries. To that end, the goal of this project is to realize a new green pathway enabling the high-precision deposition of ultra-thin nanoporous films. A molecular layer deposition (MLD) approach is proposed to construct films that feature a wide and tunable range of porosity in a single-step solvent-free coating process. This project represents a major step towards realizing the vapor-phase synthesis of porous organic frameworks (POFs) and will pave the way to integrating these films into energy efficient and highly selective filters for water purification, gas and liquid separation systems, and implantable bioartificial organs and drug delivery systems. The proposed work will create a novel manufacturing process, as it enables the synthesis of POFs that have not yet been processed as thin films. Additionally, the proposed research pathway allows for studying the physical and chemical properties of these frameworks, essential for developing fabrication processes with low environmental impact and energy footprint. The principal investigator (PI) of this study will leverage their unique materials processing platform and separation science expertise to integrate organic frameworks as active layers in high-efficiency molecular separation technologies. A priority of this project is to translate research findings into educational and outreach activities, engaging underrepresented K-to-graduate level students in STEM by exploring advanced concepts in molecular engineering. Summer programs for undergraduate and high school students will expose students to the fundamentals of reaction engineering, inspiring them to pursue research-oriented careers and become lifelong learners - a critical need highlighted in the National Science Foundation's 10 Big Ideas. All the educational components developed in this project will be maintained on an online portal to help increase public literacy pertaining to molecular and macromolecular engineering. The goal of this project is to tackle the challenges associated with the bottom-up synthesis of porous organic frameworks (POFs) by dry polymerization of polyfunctional monomers that have limited solubilities or in cases where their polymers are solvent intractable. By investigating the vapor phase processing parameters for a solvent-free polymerization pathway, a new platform for the in-situ synthesis of covalent porous frameworks will be developed. To realize dry polymerization of organic frameworks, two different polycondensation schemes (oxidative and imine-based) will be studied within a molecular layer deposition (MLD) process. Because no known dry routes to deposition of thin-film POFs have been reported, the current project will create new knowledge pertaining to processing these materials with molecular precision. By navigating the space of parameters governing polymerization reaction network rates, chemical composition and porosity of the growing films can be controlled to tune film permeability and selectivity based on the target separation application. To achieve this objective, the parameters that control the oxidative polycondensation reactions will be identified using Scholl's scheme, then the role monomer chemistries play in MLD processing will be evaluated, and lastly the in-situ synthesis and integration of these porous frameworks for nanofiltration applications will take place. A similar approach will be taken for second set of imine polycondensation reactions. Congruent with the proposed research plan, significant effort will be placed on integrating research and teaching activities to foster a reciprocal relationship between the two. Outreach and educational activities will strive to enhance the participation of students from minority and underrepresented groups in academia in research topics relevant to materials processing, surface science, and molecular engineering. A summer program, informed by research, will be developed to improve public science literacy and to attract students to research in molecular engineering. A new interdisciplinary course centered on thin-film processing for semiconductor manufacturing is planned. The resulting educational content of this course, the outreach activities, and summer programs will be available to the public via the University of Nebraska-Lincoln public digital library, Digital Commons. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.