Events
Luminescent metal-organic frameworks (MOFs); a nanolaboratory for photophysics
February 7, 2012 at 3pm/36-428
Mark Allendorf
Sandia National Laboratories
Abstract:
Metal-organic frameworks (MOFs) are a diverse class of crystalline supramolecular materials characterized by rigid, nanoporous structures and an exceptional level of synthetic versatility. Since the organic component of MOFs, referred to as the “linker,” is often an aromatic molecule, many are highly luminescent. This property has spawned a broad range of research aimed at developing MOFs for applications such as chemical sensing, imaging, and labeling, as well as interest in electronic device applications involving charge transfer. In spite of this high level of activity, efforts to understand the structural factors influencing MOF luminescence have been quite limited. It is clear, however, that if MOFs are to realize their potential for rational design of functional luminescent materials, a much-improved level of understanding is necessary. Fortunately, their highly ordered structure and tunable properties enable them to serve as a kind of “nanolaboratory,” in which photophysical phenomena can be systematically probed with a high degree of precision.
This presentation will describe a new paradigm for understanding the influence of structure on the photo- and radioluminescent properties of MOFs, which resemble proteins in the sense that interactions among the components of the framework at several length scales and structural levels influence the luminescence. This new hierarchy accounts for molecular, inter-linker, and structural flexibility effects, as well as contributions to the luminescence from guest molecules. We used a diverse suite of MOFs to systematically probe the influence of these structural features on the luminescence, which was probed via steady-state and time-dependent spectroscopies. The results demonstrate that the luminescence spectrum and timing are highly sensitive not only to the local environment of the organic linker, but also to structural features at higher length scales. Examples of how this knowledge can be harnessed to create MOF-based materials for chemical, radiation, and thermal sensing applications will be described. Finally, the implications of this research for employing MOFs in excitonic devices will be discussed; in particular, the results provide evidence for antenna effects and charge-transfer complexes that could play a role in exciton harvesting.
Bio:
Dr. Mark D. Allendorf is a Distinguished Member of the Technical Staff at Sandia and holds a PhD in inorganic chemistry from Stanford University. At Sandia, he leads efforts to develop both the fundamental science and applications of metal-organic frameworks and related materials. Currently, his research includes projects focused on chemical sensing, radiation detection, hydrogen storage, gas separations, and charge transfer. He is President Emeritus and Fellow of The Electrochemical Society and has won multiple Sandia awards for leadership and teamwork. His research involves postdoctoral fellows, students, and Sandia technical staff members and has more than 130 publications.
