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Modulating the structures of subnanometric metal clusters at the atomic level is a great synthetic and characterization challenge in catalysis. Here we show how the catalytic properties of subnanometric Pt clusters (0.5-0.6 nm) confined in the sinusoidal 10R channels of purely siliceous MFI zeolite modulate upon introduction of partially reduced Sn species that interact with the noble metal at the metal/support interface. The low mobility of Sn in H2 over an extended period of time (>6 h) even at high temperatures (e.g. 600 ⁰C), which is determined by only a few additional Sn atoms added to the Pt clusters. Such structural features, which are not immediately visible by conventional characterization techniques and can be laid out after combination of in situ EXAFS, HAADF-STEM and CO-IR data, is key to provide one-order of magnitude lower deactivation rate in the propane dehydrogenation reaction while maintaining high intrinsic (initial) catalytic activity. Pt foil a12 2.763 ± 0

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.

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The encapsulation of subnanometric metal entities (isolated metal atoms and metal clusters with a few atoms) in porous materials such as zeolites can be an effective strategy for the stabilization of those metal species and therefore can be further used for a variety of catalytic reactions. However, due to the complexity of zeolite structures and their low stability under the electron beam, it is challenging to obtain atomic-level structural information of the subnanometric metal species encapsulated in zeolite crystallites. In this protocol, we would like to show the application of a scanning transmission electron microscopy (STEM) technique that records simultaneously the high-angle annular dark-field images (HAADF) and integrated differential phase contrast images (iDPC) for structural characterization of subnanometric Pt and Sn species within MFI zeolite. The approach relies on the use of a computational model to simulate results obtained under different conditions where the metals are present in different positions within the zeolite. This imaging technique allows to obtain simultaneously the spatial information of heavy elements (Pt and Sn in this work) and the zeolite framework structure, enabling us to directly determine the location of the subnanometric metal species. Moreover, we will also present the combination of other spectroscopy techniques as complimentary tools for the STEM-iDPC imaging technique in order to obtain global understanding and insights on the spatial distributions of subnanometric metal species in zeolite structure. These structural insights can provide guidelines for rational design of uniform metal-zeolite materials for catalytic applications.

The potential applicability of high-resolution electron microscopy (HREM), in combination with image analysis and image simulation tools, to retrieve structural information from nanometre-sized particles present in oxide-supported metal and oxide catalysts is analysed. Specifically, the possibilities and limitations of this technique to determine features such as the size, morphology and chemical nature of the particles, their surface structure and their structural relationship with the support are considered through the discussion of several examples.The interpretation of a series of HREM images of Pt and Rh catalysts supported on cerium oxides after treatments under different redox environments illustrates the case of highly dispersed metals. In addition, the results obtained in this study provide an approximate picture of the evolution of metal-support interaction effects in this family of catalysts, which is closely related to three-way catalysts (TWCs). The results of a nanostructural investigation of two catalyst systems, one consisting of MgO-supported neodymia clusters and the second of vanadium-magnesium oxide also supported on MgO, provide the examples for supported oxide catalysts. These find application in oxidation reactions. For the former, the growth of neodymia in the form of rounded patches in a parallel orientation relationship with the support has been observed. For the vanadiacontaining catalysts, the formation of a weakly ordered MgV 2 O 4 spinel surface phase on the MgO support crystallites, after exposure to typical reaction conditions in the oxidative dehydrogenation of propane, has been confirmed. The structural relationship at the spinel/MgO interface has also been established. Copyright

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The synthesis and reactivity of single metal atoms in a low‐valence state bound to just water, rather than to organic ligands or surfaces, is a major experimental challenge. Herein, we show a gram‐scale wet synthesis of Pt11+ stabilized in a confined space by a crystallographically well‐defined first water sphere, and with a second coordination sphere linked to a metal–organic framework (MOF) through electrostatic and H‐bonding interactions. The role of the water cluster is not only isolating and stabilizing the Pt atoms, but also regulating the charge of the metal and the adsorption of reactants. This is shown for the low‐temperature water–gas shift reaction (WGSR: CO + H2O → CO2 + H2), where both metal coordinated and H‐bonded water molecules trigger a double water attack mechanism to CO and give CO2 with both oxygen atoms coming from water. The stabilized Pt1+ single sites allow performing the WGSR at temperatures as low as 50 °C.