CAREER: Theory-Guided Design of Porous Organic Frameworks for Energy Conversion and Storage

Western Washington University, Bellingham WA

Investigators

Abstract

NONTECHNICAL SUMMARY This CAREER award supports computational and theoretical research to develop and apply specialized computer simulations to understand how electrons and energy are transferred within a class of materials known as covalent organic frameworks. These materials can be porous at the scale of single molecules, making them strong candidates for the storage of gasses and for separation technologies; preliminary work suggests that they may also provide a valuable scaffold for applications in renewable energy harvesting and conversion. For example, these frameworks of molecules may be used to anchor and orient the light-absorbing parts of a material for efficient energy transfer or increased energy storage density. This project will accelerate the development of this promising class of materials for renewable energy applications by providing a targeted computer simulation strategy to predict the behavior of electrons in these materials after they absorb visible light. The PI mentors a team of undergraduate and Master's student researchers in the development and application of simulations. Their cross-disciplinary training will contribute to the preparation of a robust STEM workforce in the physical and computational sciences. The goals of this research also directly integrate with the PI's efforts as an educator to enhance energy literacy among undergraduate and high school students. Educational simulations that illustrate the energy conversion mechanisms at play in the materials studied here will be developed in collaboration with student researchers; employed in the PI's energy, materials, and chemistry classrooms; and shared with the public to broaden access to energy science resources. These research and educational objectives are directly linked to an undergraduate student-driven energy literacy outreach initiative, recently established by the PI at WWU, which will be further enhanced through development into a service learning program. TECHNICAL SUMMARY This CAREER award supports computational and theoretical research on optical and electronic properties of covalent organic frameworks. The rational design of photoactive and electroactive covalent organic frameworks is hindered by a lack of predictive models at extended length and time scales to link the optical and electronic properties of these frameworks to their underlying structure. This project aims to address this knowledge gap through the development of a multireference computational approach that strategically links semiempirical ground- and excited-state electronic structure calculations to predict photophysical properties, energy transfer, and charge carrier mobility in electroactive and photoactive covalent organic frameworks. The approach builds on the PI's implementation of a time-independent approach to low-lying excited states in density-functional tight-binding to incorporate charge-transfer excitations as well as couplings between electronic states in these materials. This constrained density-functional tight-binding based configuration interaction (CDFTB-CI) approach will be deployed to study photoexcitation and electron/energy transfer in selected covalent organic frameworks as singlet fission materials and as photoswitchable energy storage materials. The models developed and applied here will also provide a partial blueprint for computational materials scientists to quantify links between structural and electronic properties in other topologically complex environments such as metal-organic frameworks. This project will directly enable the training and mentoring of a diverse group of 15-20 undergraduate and masters-level research students at a primarily undergraduate institution. To broaden the educational impact of this work and to communicate energy conversion and storage concepts to the public, the PI will create and assess the effectiveness of augmented materials simulations that support fluency in mathematical and physical models of energy conversion. This project will also establish a sustainable trajectory for the PI's Energy Ambassadors initiative, a program that couples undergraduate research across the science, engineering, economics, policy, and business of energy with cross-disciplinary communication skill-building and K-12 outreach. The Division of Materials Research and the Division of Chemistry contribute funds to this award. 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.