Mark Lipke

Rutgers University

Title:

Redox Behavior and Reactivity of Porphyrin-Walled Nanocages and Other Molecular Materials

Abstract:

Nanoporous materials, such as MOFs, COFs, and discrete nanocages, are increasingly targeted as tunable supports for molecular electrocatalysts. The pores of these materials provide new opportunities for tuning catalytic activity but also raise challenging mechanistic questions since the confined pore environment must rearrange to accommodate the movement of charge during electrocatalytic processes. This talk will describe the development of porphyrin-walled nanocages as soluble model structures for examining how nanoconfined environments respond to redox changes. The cages exhibit rich redox-responsive host-guest chemistry that was used to probe proton-coupled and other cation-coupled redox processes, providing insights about how key steps of electrocatalytic transformations might be altered in nanoporous materials. The catalytic activity of metal sites embedded in the walls of the cages will also be discussed. Easily synthesized nanocages developed by the Lipke group show good activity for electrochemical CO₂ reduction, and the formation of host-guest complexes between these cages and fullerenes was found to substantially alter their activity and selectivity, revealing unexpected influences on the catalytic behavior of these porous structures. Time permitting, the redox behavior, electronic structure, and physical properties of electronically delocalized cobalt complexes will be described, with a focus on how these complexes might be useful for developing self-assembled conductive materials.

Bio:

Mark Lipke earned his B.S. in chemistry from Case Western Reserve University in 2008, where he first got involved in research working with Professor John Protasiewicz. Mark then earned his PhD in 2013 studying novel ruthenium-silane complexes in the group of Don Tilley at UC Berkeley, before moving on to a postdoc at Northwestern University studying redox-responsive molecular nanomaterials with Sir Fraser Stoddart. Professor Lipke began his independent career at Rutgers (New Brunswick) in 2017 where his research combines his interests in transition metal reactivity and redox-active nanomaterials.