Pressure-induced Breathing in Microporous Coordination Polymer Thin Films: A Mechanism for Gas Sensing

University Of Alabama Tuscaloosa, Tuscaloosa AL

Investigators

Abstract

With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, and partial co-funding from the Established Program to Stimulate Competitive Research (EPSCoR), Gregory Szulczewski and his group at the University of Alabama - Tuscaloosa are designing and characterizing special polymers intended for use in thin-film sensors for detection and quantitation of volatile organic compounds (VOCs). The work seeks better understanding of how the polymer swelling process differs from that in bulk solids. These insights in turn will be applied to the development of a new type of gas sensor technology, that, if successful, has potential for applications in the environmental, industrial, and agricultural sectors. The project will engage K-12 students, seeking to motivate them to consider studying science; activities will include scientific demonstrations and hands-on activities conducted at a local science museum and schools. Summer research projects are planned to engage students from HBCUs (Historically Black Colleges and Universities) who seek careers in science, technology, engineering and math. Microporous coordination polymers, or MCPs, have emerged as potential materials for catalysis, gas storage, gas separations, and chemical sensing. Critical to these applications is the well-defined porosity of the material. In some instances the structure is rigid, but some MCPs exhibit a breathing phenomenon, wherein lattice expansion can occur above a certain pressure of a given VOC, allowing rapid diffusion of the guest into the newly modified microporous host. The Szulczewski group aims to identify key design parameters for the synthesis of breathing MCP thin films and to establish the key structure-function relationships that will advance the basic understanding of lattice expansion. Specifically, the team will measure adsorption/desorption isotherms of VOCs in thin films of “breathing” MCPs to identify the “gate-opening” pressure. They will further probe the impact of varying MCP building blocks (i.e., metal ions and organic linkers) as well as the role of defects, film thickness, and general morphology on the mechanism of lattice expansion. Using parallel impedance measurements and an iterative feedback loop, these fundamental studies are targeting development of a new type of gas sensor technology. 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.