NH3-Selective Catalytic Reduction (NH3-SCR) is a widely used technology for NO x reduction in the emission control systems of heavy duty diesel vehicles. Copper-based ion exchanged zeolites and in particular Cu-SSZ-13 (CHA framework) catalysts show both exceptional activity and hydrothermal stability for this reaction. In this work, we have studied the origin of the SCR activity of Cu-SSZ-13 as evidenced from a combination of synchrotron-based and laboratory techniques. Synchrotron-based in situ XAFS/XRD measurements were used to provide complementary information on the local copper environment under realistic NH3-SCR conditions. Crucial then to the catalytic activity of Cu-SSZ-13 is the local environment of the copper species, particularly in the zeolite. Cu-SSZ-13 contains mononuclear Cu2+ species, located in the face of the double-6-ring subunit of the zeolite after calcination where it remains under reaction conditions. At lower temperatures (with low activity), XAFS and XRD data revealed a conformational change in the local geometry of the copper from a planar form toward a distorted tetrahedron as a result of a preferential interaction with NH3. This process appears necessary for activity, but results in a stymieing of activity at low temperatures. At higher temperatures, the Cu2+ possess a local coordination state akin to that seen after calcination.

High resolution synchrotron radiation x-ray powder diffraction (HR-XRPD) combined with Hf L3edge extended x-ray absorption fine structure (EXAFS) allowed to determine the structure of Hf-UiO-66 metal-organic framework (MOF) showing that it is iso-reticular to Zr-UiO-66 MOF [J. Am. Chem. Soc. 130, 13850 (2008)]. Thermal gravimetric measurements (coupled with mass spectroscopy) and temperature dependent synchrotron radiation XRPD proved the high thermal stability of the new MOF. The Langmuir surface area (849 m 2 /g) combined with the high stability of the UiO-66 framework and with the high neutron absorption cross section of Hf suggest that among all microporous crystalline materials the new Hf-UiO-66 MOF possesses the physical and chemical requirements for the interim storage of radioactive waste in a much safer way than is currently available. The first results proving the synthesis of a MOF material with UiO-66 topology realized by B-containing linker are also reported, allowing a further improvement of the neutron shielding power of these class of materials.

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Crystallite size effects can influence the performance of battery materials by making the structural chemistry deviate from what is predicted by the equilibrium phase diagram. The implications of this are profound: the properties of many battery materials should be reassessed. Sodium ion battery anodes made from nanocrystalline bismuth form different phases during electrochemical cycling compared to anodes with larger crystallites. This is due to the formation of a metastable cubic polymorph of Na 3 Bi on the crystallite surfaces. The structural differences (weaker Na−Bi bonds, different coordination of Na to Bi) between the metastable cubic Na 3 Bi phase found in the nanocrystals and the hexagonal equilibrium polymorph which dominates the larger crystallites offer an explanation for the improvements in cycling behavior observed for the nanostructured anode.

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