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Active Sites in Cr(III)-Based Ethylene Polymerization Catalysts from Machine-Learning-Supported XAS and EPR Spectroscopy
(2024)Angewandte Chemie. International EditionThe ethylene polymerization Phillips catalyst has been employed for decades and is central to the polymer industry. While Cr(III) alkyl species are proposed to be the propagating sites, there is so far no direct experimental evidence for such proposal. In this work, by coupling Surface organometallic chemistry, EPR spectroscopy, and machine learning-supported XAS studies, we have studied the electronic structure of well-defined silica-supported ...Journal Article -
Probing the Nature of Surface Hydrides by Deuterium Quadrupolar Parameters: A Case Study on Silica-Supported Zirconium Hydrides
(2024)Helvetica Chimica ActaSupported metal hydrides are key reactive intermediates in various catalytic processes, such as hydrogenation and dehydrogenation, but are often challenging to characterize spectroscopically. Here, deuterium solid state nuclear magnetic resonance spectroscopy is used to understand the structure of the corresponding silica-supported zirconium hydrides after H/D exchange as an illustrative example of supported metal hydrides, which have ...Journal Article -
Small Cobalt Nanoparticles Favor Reverse Water-Gas Shift Reaction Over Methanation Under CO2 Hydrogenation Conditions
(2023)Angewandte Chemie. International EditionCobalt-based catalysts are well-known to convert syngas into a variety of Fischer-Tropsch (FTS) products depending on the various reaction parameters, in particular particle size. In contrast, the reactivity of these particles has been much less investigated in the context of CO2 hydrogenation. In that context, Surface organometallic chemistry (SOMC) was employed to synthesize highly dispersed cobalt nanoparticles (Co-NPs) with particle ...Journal Article -
Surface Sites and Ligation in Amine-capped CdSe Nanocrystals
(2023)Angewandte Chemie. International EditionConverting colloidal nanocrystals (NCs) into devices for various applications is facilitated by designing and controlling their surface properties. One key strategy for tailoring surface properties is thus to choose tailored surface ligands. In that context, amines have been universally used, with the goal to improve NCs synthesis, processing and performances. However, understanding the nature of surface sites in amine-capped NCs remains ...Journal Article -
Identification of Favorable Silica Surface Sites for Single-Molecule Magnets
(2023)Helvetica Chimica ActaIndustrial data storage application based on single-molecule magnets (SMMs) necessitates not only strong magnetic remanence at high temperatures but also requires the implementation of SMMs into a solid material to increase their durability and addressability. While the understanding of the relationship between the local structure of the metal and the resulting magnetic behavior is well understood in molecular systems, it remains challenging ...Journal Article -
Lithium Promotes Acetylide Formation on MgO During Methane Coupling Under Non-Oxidative Conditions
(2023)Angewandte Chemie. International EditionA prototypical material for the oxidative coupling of methane (OCM) is Li/MgO, for which Li is known to be essential as a dopant to obtain high C₂ selectivities. Herein, Li/MgO is demonstrated to be an effective catalyst for non-oxidative coupling of methane (NOCM). Moreover, the presence of Li is shown to favor the formation of magnesium acetylide (MgC₂), while pure MgO promotes coke formation as evidenced by solid-state ¹³C NMR, thus ...Journal Article -
Visualizing Structural and Chemical Transformations of an Industrial Cu/ZnO/Al2O3 Pre-catalyst during Activation and CO2 Reduction
(2022)ChemCatChemThe typical industrial catalyst used for methanol synthesis is a multi-component catalyst based on Cu/ZnO/Al2O3. The synergies between various phases of this catalyst play a vital role in defining the overall catalytic function and performance. To gain insights into the role and interaction between the relevant components and phases, ex situ and in situ transmission electron microscopy (TEM) was deployed to investigate the structures and ...Journal Article -
Grafting of Group-10 Organometallic Complexes on Silicas: Differences and Similarities, Surprises and Rationale
(2022)Helvetica Chimica ActaSurface organometallic chemistry (SOMC) represents a unique synthetic platform for the preparation of model heterogeneous catalysts resembling those broadly applied in industry. SOMC techniques usually rely on the grafting of tailored molecular precursors onto the surface OH groups of oxide supports. The development of such precursors and the understanding of their reactivity with the supports are therefore crucial for the development of ...Journal Article -
Elucidation of Metal Local Environments in Single-Atom Catalysts Based on Carbon Nitrides
(2022)SmallThe ability to tailor the properties of metal centers in single-atom heterogeneous catalysts depends on the availability of advanced approaches for characterization of their structure. Except for specific host materials with well-defined metal adsorption sites, determining the local atomic environment remains a crucial challenge, often relying heavily on simulations. This article reports an advanced analysis of platinum atoms stabilized ...Journal Article -
Olefin Metathesis Catalysts Generated In Situ from Molybdenum(VI)-Oxo Complexes by Tuning Pendant Ligands
(2022)Chemistry - A European JournalTailored molybdenum(VI)-oxo complexes of the form MoOCl2(OR)2(OEt2) catalyse olefin metathesis upon reaction with an organosilicon reducing agent at 70 °C, in the presence of olefins. While this reactivity parallels what has recently been observed for the corresponding classical heterogeneous catalysts based on supported metal oxide under similar conditions, the well-defined nature of our starting molecular systems allows us to understand ...Journal Article