The tunable architectures and intrinsic porosity of metal organic frameworks (MOFs) are uniquely suited for adsorption-based applications such as heterogeneous catalysis. By targeting specific topologies and incorporating strategically placed catalytic sites at node and/or linker positions, these porous solid state networks can be designed, in theory, for specific reactions with optimized selectivity and efficiency. Despite advances in developing new catalytically active frameworks, fundamental understanding of their adsorption-based processes and reaction mechanisms is often limited. Spectroscopy methods are commonly used to obtain this molecular-level information. Conventional X-ray absorption spectroscopy (XAS) is a powerful tool for probing reactive metal sites in heterogeneous catalysts, including MOFs, but it still has significant limitations that curb its application to MOF adsorption processes and reactions. Here we demonstrate the use of X-ray emission spectroscopy (XES) methods for probing host-guest interactions in MOF materials. Monitoring specific emissive pathways through energy-resolved partial fluorescence yield detection can reveal quantitative spin state information and coordinated guest molecule identity of framework metal sites. XES studies of several MOF examples will be presented along with their corresponding conventional XAS data for comparison.

X-ray emission spectroscopy studies of metal–organic frameworks

256th National Meeting (2018)

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