CAREER: Framework Topology Dependent Photophysical Properties of Chromophore Assemblies within Metal-Organic Frameworks

Southern Illinois University At Carbondale, Carbondale IL

Investigators

Abstract

In this CAREER project, funded by the Chemical Structure, Dynamics, & Mechanisms-B Program of the Chemistry Division, Professor Pravas Deria of the Department of Chemistry & Biochemistry at Southern Illinois University Carbondale is developing assemblies of highly colored organic molecules carefully arranged in specific structures (known as metal-organic frameworks). These Metal-organic frameworks have unique properties when they react with light. The goal of this research is to make framework compositions with the ability to capture and specifically channel light for efficient light harvesting and conversion into stored chemical energy. The knowledge gained through this CAREER research will have a broad impact in southern Illinois by augmenting young student's (high school and below) perception towards basic science. Professor Deria will recruit regional high school (HS) students into a two-week chemistry research camp, where they will be introduced to fundamental scientific research --including hands-on experience with exciting modern instrumentation. Middle school students will be involved in demonstration of the 'Science of Colors' with molecular pigments in biology at a local Science Center. These educational programs will provide firsthand experience to inspire students to choose science careers. The project lies at the interface of inorganic, organic, and physical chemistry, and is well suited for the education of scientists at all levels as the project has applications to solar to fuels, clean energy technologies. Achieving photosystem II-like photophysical behavior for efficient photonic energy harvesting in artificial chemical assemblies is a challenge due to demanding supramolecular synthetic designs. Precise and controllable organization of pigments is a prerequisite to achieving new compositions that function differently than simple chromophore aggregates. Porous crystalline metal-organic frameworks (MOFs) offer unique platforms to develop well-defined, solution-stable molecular chromophore assemblies with efficient photon energy transducing functionality. However, the design and control of desirable photosystem II-like photophysical behavior in well-defined MOFs is at an early stage of discovery. Basic rules governing exciton formation, long-range exciton propagation, and directing exciton splitting into work-producing charges within these synthetic framework-assemblies need to be fully established. This CAREER project explores novel MOF compositions that control excitonic structure and dynamics as a function of framework topology and elucidates how chromophore electronic structure and excited-state symmetry impacts exciton delocalization and migration. The research may unveil the critical factors that modulate singlet-triplet intersystem crossing quantum yields. 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.