Conductive Dithiolene-Based Metal Organic Frameworks (MOFs) with Tunable Transport Properties

University Of Southern California, Los Angeles CA

Investigators

Abstract

Non-technical abstract: Metal-organic frameworks (MOFs) are crystalline nanoporous materials composed of metal ions or clusters linked by organic molecules. Due to their precisely controlled nano-enviroments and synthetic tunability, MOFs have emerged as a promising class of materials with adjustable properties However, the insulating nature of MOFs has limited their use in technologies that require charge transport, such as electronics. This project, which is supported by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, builds on previous research in the Marinescu group that has shown that some two-dimensional extended frameworks display high electrical conductivity. With this award, the understanding of the factors that govern the transport properties of these frameworks is advanced by characterizing and changing the electronic environment, as well as studying the bulk properties of these MOFs. The synthetic tunability of these frameworks allows for excellent control of their coordination environment, which facilitates structure-activity studies. The educational components of this award integrate aspects of chemistry related to energy and materials applications researched in the laboratory and reach middle/high school students and teachers, as well as postdoctoral scholars, graduate, and undergraduate students, with a focus on women, an underrepresented group in science. Technical abstract: With this project, which is supported by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, the use of redox active ligands, such as dithiolenes, is investigated as a means to facilitate charge transport through MOFs. Previous research in the Marinescu group has demonstrated that two-dimensional cobalt-containing MOFs based on benzenehexathiolate and 2,3,6,7,10,11-triphenylenehexathiolate ligands can be produced with high degree of crystallinity. These MOFs that contain extensive delocalization of the metal and ligand orbitals exhibit high electrical conductivity, and this project tests the PI’s fundamental hypothesis that the transport properties of MOFs can be modulated through a synthetic, bottom-up approach with an emphasis on tuning the coordination sphere effects and incorporation of guest-species and dopants into these porous architectures. Several structurally analogous frameworks are investigated to understand the underlying structural features and mechanisms, which promote and control the conductivity of these MOFs. The electronic environment of these proposed MOFs are modulated by changing the identity of the metal center, its oxidation state, and charge compensating cations. The studies provide information on how the local environment and the bulk properties of the metal dithiolene frameworks affect their conductivity, which is instrumental in the development of design principles to generate conductive MOFs. The educational activities associated with this award are multifaceted and involve Los Angeles middle/high-school students and teachers, as well as graduate and undergraduate students from USC: the PI (1) leads a mentoring program for women at the undergraduate level to increase the participation of women in science; and (2) develops a summer workshop for teachers from local schools where hands-on experiments are performed. Most importantly, students involved in these efforts develop a long-lasting culture of contributing to their scientific and non-scientific communities. 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.