Synthetic control over redox-state and morphology in electronically complex coordination polymers

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Non-Technical Summary Technological advances are built upon the discovery of new materials and new methods to control their properties and function. Recent years have seen a surge of interest in such a class of materials known as coordination polymers. These materials have the advantage of being porous and extremely tunable. In addition to major advances in using these materials for gas storage, catalysis, and sensing, there is increasing focus on using their electronic properties for applications in new devices or for different technologies. However, understanding and control over the electronic properties of coordination polymers is still limited. This project, which is supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, specifically involves the synthesis and study of coordination polymers with intrinsic building blocks that have the ability to hold or lose electrons. The ability to tune the electronics of these materials offers the promise of exciting new properties and applications. Furthermore, the porosity of these materials allows the possibility to modulate their properties over a much wider range than standard materials candidates. Thus, researchers at the University of Chicago design a broad new class of materials with modular and tunable properties for a wide variety of applications. In parallel with these research efforts, the award supports a local conference which includes undergraduate students, graduate students, and local postdoctoral researchers. This conference builds a community of researchers in the Chicago area as well as links to ongoing efforts with younger students to increase scientific communication and literacy. Technical Summary Coordination polymers (CPs) and metal-organic-frameworks (MOFs) with electronic properties such as conductivity and/or magnetism are an exciting new class of materials with myriad applications. Part of the appeal of these materials arises from their innate properties, namely porosity and reticular structure. However, CPs are also uniquely poised as electronic/magnetic materials; the molecular nature of CP nodes and linkers enables synthetic tuning of physical properties. Furthermore, facile intercalation of counterions coupled with redox-active molecular motifs enables unparalleled degrees of electronic flexibility spanning many different redox-states. These properties have stimulated immense interest in synthesizing new electronically complex CPs and MOFs. Despite enormous progress and new materials with truly remarkable properties, there remain large synthetic challenges in the field of conducting or magnetic CPs. Namely, most newly synthesized materials are isolated in a serendipitous oxidation state; controlling the morphology of formed materials, for instance to incorporate them into devices, is still a major challenge. There is now a substantial need to tune and control properties via precise synthetic modulation of redox-state and morphology. As such, the main focus of this project, which is supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, is to discover robust synthetic approaches to control CP redox-state and morphology, particularly in S-based materials. Specifically, researchers at the University of Chicago explore variable points of redox-modulation, either before CP synthesis, in-situ during CP formation, or postsynthetically, to control electronic or magnetic properties. A key hypothesis underlying the research is that the solubility of CP building blocks or oligomers is related to their redox-state and hence charge, and thus that redox modulation also enables control over CP morphology. The successful realization of this research is expected to provide a set of tools for tuning and applying electronically complex CPs in many different areas.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.