Mn and Fe ions and oxo clusters in ZSM-5: pushing the limits of X-ray spectroscopy

X-ray spectroscopic techniques are important tools for the characterization of metal ions, clusters and nanoparticles in zeolites. A major limitation in X-ray absorption spectra is the intrinsic broadening due to core hole lifetime effects. Using high-energy resolution fluorescence detection (HERFD), this intrinsic broadening is removed, revealing new fine structure. In addition, we will show that the use of circular polarized X-rays can be a useful tool to determine the aggregation of metal ions. We present results obtained using these novel X-ray spectroscopic techniques, using Fe-ZSM-5 and Mn-ZSM-5 systems as showcases. The prospects for these techniques to become "standard" tools for catalysis's research will be discussed