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Ultrasmall silver clusters in reduced state are difficult to synthesize since silver atoms tend to rapidly aggregate into bigger entities. Here, we show that dimers of reduced silver (Ag) are formed within the framework of a metal–organic framework provided with thioether arms in their walls (methioMOF), after reduction with NaBH of the corresponding Ag-methioMOF precursor. The resulting Ag-methioMOF catalyzes the methanation reaction of carbon dioxide (CO to CH hydrogenation reaction) under mild reaction conditions (1 atm CO, 4 atm H, 140 °C), with production rates much higher than Ag on alumina and even comparable to the state-of-the-art Ru on alumina catalyst (Ru–AlO) under these reaction conditions, according to literature results.

Developing precious-metal-free electrocatalysts for the hydrogen evolution reaction (HER) is crucial to establishing H2 produced from renewable energy sources as an alternative energy carrier to fossil fuels. Amorphous molybdenum sulfide-based materials are promising candidates that provide highly active HER electrocatalysts by introducing active sites at both the edge positions and the typically inactive basal planes. Herein, we report an innovative bottom-up synthesis of amorphous molybdenum sulfides using molecular complexes with Mo3S4 and Mo3S7 cluster cores as building entities. The ability to control the precursor of choice has made it viable to enhance the HER activity of these materials. Furthermore, the tunability of the atomic composition of the molecular cluster precursors allows the modification of the derived materials with atomic-scale precision, enabling us to track the synthesis mechanism and, in combination with Density Functional Theory (DFT) calculations, to decipher the nature of the HER active sites.

The dynamic nature of the copper cations acting as active sites for selective catalytic reduction of nitrogen oxides with ammonia is investigated using a combined theoretical and spectroscopic approach. Ab initio molecular dynamics simulations of Cu-CHA catalysts in contact with reactants and intermediates at realistic operating conditions show that only ammonia is able to release Cu+ and Cu2+ cations from their positions coordinated to the zeolite framework, forming mobile Cu+(NH3)2 and Cu2+(NH3)4 complexes that migrate to the center of the cavity. Herein, we give evidence that such mobilization of copper cations modifies the vibrational fingerprint in the 800–1000 cm–1 region of the IR spectra. Bands associated with the lattice asymmetric T-O-T vibrations are perturbed by the presence of coordinated cations, and allow one to experimentally follow the dynamic reorganization of the active sites at operating conditions.

The catalytic properties of sub-nanometer Cu clusters are modified by interactions with inorganic supports used for their stabilization. In this work, the reactivity towards O dissociation of Cu and Cu clusters confined within the cavities of the CHA zeolite is theoretically investigated by means of periodic DFT calculations. Increasing the Al content in the zeolite framework not only modifies the cluster morphology, but also leads to a decrease in the electronic density available on the supported Cu clusters, which in turn leads to higher activation energies for O dissociation. Together with the cluster size and shape, the Si/Al ratio in the zeolite support appears as a potential parameter to finely tune the stability and oxidation properties of Cu-based catalysts.

The partial oxidation of methane to methanol with molecular Oat mild reaction conditions is a challenging process, which is efficiently catalyzed in nature by enzymes. As an alternative to the extensively studied Cu-exchanged zeolites, small copper clusters composed by just a few atoms appear as potential specific catalysts for this transformation. Following previous work in our group that established that the reactivity of oxygen atoms adsorbed on copper clusters is closely linked to cluster size and morphology, we explore by means of DFT calculations the ability of bidimensional (2D) and three-dimensional (3D) Cuand Cuclusters to oxidize partially methane to methanol. A highly selective Eley-Rideal pathway involving homolytic C-H bond dissociation and a non-adsorbed radical-like methyl intermediate is favored when bicoordinated oxygen atoms, preferentially stabilized at the edges of 2D clusters, are available. Cluster morphology arises as a key parameter determining the nature and reactivity of adsorbed oxygen atoms, opening the possibility to design efficient catalysts for partial methane oxidation based on copper clusters.

Subnanometric metal species confined inside the microporous channels/cavities of zeolites have been demonstrated as stable and efficient catalysts. The confinement interaction between the metal species and zeolite framework has been proposed to play the key role for stabilization, though the confinement interaction is elusive to be identified and measured. By combining theoretical calculations, imaging simulation and experimental measurements based on the scanning transmission electron microscopy-integrated differential phase contrast imaging technique, we have studied the location and coordination environment of isolated iridium atoms and clusters confined in zeolite. The image analysis results indicate that the local strain is intimately related to the strength of metal-zeolite interaction and a good correlation is found between the zeolite deformation energy, the charge state of the iridium species and the local absolute strain. The direct observation of confinement with subnanometric metal species encapsulated in zeolites provides insights to understand their structural features and catalytic consequences.

© The Royal Society of Chemistry. The selective incorporation of isolated framework Lewis acid sites at specific crystallographic positions in high-silica zeolites was achieved by applying a rationalized post-synthetic grafting methodology. The removal of framework Ge atoms from a Ge-BEC zeolite with low concentrations of Ge in the framework (Si/Ge ∼ 150) followed by grafting allows the synthesis of Sn-BEC zeolites with Sn atoms positionally biased into the double-4-ring (D4R) crystallographic positions of the BEC framework. Spectroscopic characterization using solid-state nuclear magnetic resonance (NMR) coupled with theoretical calculations revealed that Sn atoms preferentially form open Sn sites in the D4R of Sn-BEC. This observation was supported by IR spectra of adsorbed deuterated acetonitrile (CD3CN), a known titrant of Sn sites in zeolites. The catalytic implications of selective incorporation of open Sn sites in Sn-BEC were probed using the Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reaction. Although the MPVO turnover rates normalized by the total number of open Sn sites were comparable on Sn-BEC and a conventional Sn-Beta catalyst synthesized in fluoride media (Sn-Beta(F)), Sn-BEC demonstrated higher per gram reaction rates because of its larger fraction of open sites compared to Sn-Beta(F). These results highlight the advantage of placing active sites in targeted locations within a zeolite structure. The methodology presented here to selectively place catalytic active sites via sacrificial heteroatoms, such as Ge, can be generalized for the design of many other tetrahedrally-coordinated metal-containing zeolites. This journal is

As one of the most influential scientists in the field of heterogeneous catalysis and materials science, Prof. Avelino Corma has made significant contributions in many diverse fields, spanning over solid catalysts for petrochemistry, solid catalysts for production of fine chemicals, synthesis of microporous and mesoporous materials, development of inorganic-organic hybrid materials, supported metal catalysts (from isolated metal atoms to nanoclusters and nanoparticles) and photochemistry with solid materials. These experimental approaches are complemented with characterization of solid materials with advanced spectroscopy and microscopy techniques as well as theoretical calculations/modeling. The aim of this Account is to overview Avelino's distinguished scientific career and highlight the most remarkable achievements made in his research activities during >40 years. We attempt to show the evolution of Avelino's research topics in his group throughout his career and the approaches that Avelino has chosen to tackle the challenges encountered. The research paradigm developed by Avelino and his team can be inspiring to the researchers in the field of materials science who are striving to translate the knowledge generated in fundamental studies into practical applications for addressing the new scientific challenges encountered in building a sustainable world.

The mechanism of the CO oxidation reaction catalysed by planar Cu5, three dimensional (3D) Cu5, and 3D Cu8 clusters is theoretically investigated at the B3PW91/Def2TZVP level. All three clusters are able to catalyse the reaction with similar activation energies for the rate determining step, about 16-18 kcal mol-1, but with remarkable differences in the reaction mechanism depending on cluster morphology. Thus, for 3D Cu5 and Cu8 clusters, O2 dissociation is the first step of the mechanism, followed by two consecutive CO + O reaction steps, the second one being rate determining. In contrast, on planar Cu5 the reaction starts with the formation of an OOCO intermediate in what constitutes the rate determining step. The O-O bond is broken in a second step, releasing the first CO2 and leaving one bi-coordinately adsorbed O atom which reacts with CO following an Eley-Rideal mechanism with a low activation energy, in contrast to the higher barriers obtained for this step on 3D clusters. This journal is

Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This “ab-initio” analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHA-type material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.