CAREER: Two-Dimensional Covalent Organic Framework (2D COF) Membranes: A New Platform for Liquid Separations

University Of Houston, Houston TX

Investigators

Abstract

Liquid separations are central to the health and prosperity of the nation through their use in treating drinking water, manufacturing therapeutics, and purifying industrial chemicals. Current approaches to achieve these liquid separations are challenged by high energy consumption, low production rates, and imperfect separation performance. Covalent organic frameworks are polymers with ordered porous structures that can function as membranes to efficiently separate complex liquids, such as removing salt from water or filtering impurities from organic liquids. This research project will engineer ultrathin covalent organic framework membranes with tunable pore properties to achieve liquid separations based on specific characteristics of the liquids. The fundamental knowledge that is gained about engineering the properties of covalent organic framework membranes will enable them to be specifically designed to achieve more effective liquid separations for applications in the energy, environmental, and health fields. The research program is integrated with the professional development of pre-service science and math teachers who will engage in individual research projects and will develop inquiry-based curriculum for the public high schools in which they typically serve. The goal of this research is to engineer two-dimensional covalent organic framework (2D COF) membranes with tunable pore properties and to model their performance for liquid separations based on size, charge, and adsorption. Large-area membranes with varying thicknesses will be fabricated by interfacial polymerization of orthogonally soluble monomers at a confined interface. Control over 2D COF pore structure will be achieved by direct integration of variable-length monomers into 2D COFs during their controlled interfacial polymerization and by engineering the stacking of 2D COF monolayers through introduced steric hindrances. Pore surface modifications by post-fabrication chemical functionalization will enable control over pore chemistry. The separation performance of the resulting 2D COF membranes will be tested for organic mixtures and aqueous solutions, including organic solvent nanofiltration, brackish groundwater desalination, and uranium adsorption. The experimental results will be used to develop and validate pore-flow models for 2D COF membrane separations that include steric and non-steric mechanisms. Eight pre-service secondary STEM teachers from the teachHOUSTON program will engage in the research by conducting individual research projects and developing related STEM curriculum. The projects are designed to cultivate an inquiry mindset and prepare the pre-service teachers to enact inquiry-based STEM curriculum in public high schools in the greater Houston area. The research results will also be integrated into a Membrane Separations graduate course that will help close the gap in training for separation scientists from disparate chemistry and engineering fields. A water treatment learning activity will be developed to introduce new filtration concepts to the broader community and to stimulate interest in separation science. 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.