Abstract
This presentation will discuss the efforts by our research groups at Northwestern University and Argonne National Laboratory in trying to bridge homogeneous and heterogeneous catalysis through the use of supramolecular environments and porous materials, such as metal-organic frameworks (MOFs) and porous organic polymer (POPs), as platforms for deploying homogeneous catalysts.
Supramolecular assemblies are large soluble structures constructed from molecules rather than atoms as building blocks. As thermodynamically stable structures, the stability of these materials comes from marshalling multiple weak interactions in a highly reinforcing way. In this sense, supramolecular chemistry has the potential for bringing together cooperative catalytic sites, stabilizing potent reaction centers, and creating architectures that elicit reaction selectivity. Previous examples from our group include assemblies capable of catalyzing enantioselective oxidation reactions, enantioselective epoxide ring-opening, and acyl transfer reactions with applications in sensing.
As hybrid materials derived from well-defined molecular building blocks, newly emerged porous materials such as metal-organic frameworks (MOFs) and porous organic polymers (POPs) are natural solid-state 3-D versions of supramolecules. These materials have many of the desirable features of zeolites, such as high surface area and porosity, and can be similarly effective in size- and shape-selective catalysis. However, given the enormous diversity of potential structures and chemical functional groups that can be incorporated into the pores of MOFs and POPs, these porous materials have the potential to extend catalysis far beyond the realm of zeolitic chemistry to include enzyme-like behaviors such as adapted flexibility during catalysis, substrate pre-concentration effects, active-site isolation and protection, and tunable hydrophobicity. Most importantly, recent developments in MOF and POP synthesis have given rise to catalytically active materials with unprecedented stability and novel activity that were not observed in solution.
