CAS: Molecular Design of Photoactive Covalent Organic Frameworks Capable of Reductive and Oxidative Degradation of Perfluoroalkyl Substances

William Marsh Rice University, Houston TX

Investigators

Abstract

With the support of the Chemical Catalysis program in the Division of Chemistry, Professors Thomas Senftle and Rafael Verduzco of Rice University are studying the development of new photocatalytic materials for treating waters contaminated with poly- and perfluoroalkyl substances (PFAS). PFAS molecules are collectively known as “forever chemicals” because they do not break down naturally in the environment and can accumulate in water, soil, and sources of food. Given the health risks posed by such forever chemicals, new methods are urgently needed for removing PFAS contamination from our waterways. To address this problem, the research team will develop nanostructured, highly porous materials that are also photocatalytically active, enabling the simultaneous adsorption and degradation of PFAS to convert them to benign products. Specifically, the team is developing photochemically-active covalent organic frameworks (COFs) for removal of PFAS from water. COFs are fully organic macromolecules with a honeycomb-like molecular structure, and the Rice scientists will seek to engineer these materials to interact strongly with PFAS for both adsorption and photochemical degradation. This project has the potential to advance the development of low-cost approaches for remediating PFAS-contaminated water, toward ultimately developing sustainable and economically viable approaches for water treatment. The project also will establish new outreach activities. The PIs will host students from a local community college to provide hands-on laboratory experience for students who otherwise would have limited research opportunities. The PIs also will work with teachers from a local high school through a Research Experiences for Teachers (RET) program at Rice University, which will produce high-quality learning modules to bolster K-12 STEM education in the Houston area. Under this project, Drs. Senftle and Verduzco and their team will apply computational and experimental methods to develop covalent organic frameworks (COFs) as photocatalysts for the degradation of poly- and perfluoroalkyl substances (PFAS). The modular nature of COFs offers several avenues for tuning their interactions with PFAS molecules, which can be used to enhance adsorption and control catalytic degradation mechanisms. The group will study a series of COF structures with variations in backbone and side-chain functionalization, which is expected to enhance to provide knowledge of the structure-property relationships that govern photocatalytic PFAS degradation mechanisms in COFs. The combined use of simulation and experiment is expected to lead to an improved understanding of the physical mechanisms that influence COF performance both as an adsorbent and a photocatalyst. Studies will focus on clarifying the influence of optoelectronic properties at the electronic scale to better understanding molecular diffusion and adsorption at the atomic scale. The project aims to deliver new design principles for enhancing PFAS adsorption and degradation in photocatalytic COF materials. 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.