Infrared Characterization of Hydroxyl Groups on MgO:  A Periodic and Cluster Density Functional Theory Study

Chizallet, Céline; Costentin, Guylène; Che, Michel; Delbecq, and Françoise; Sautet, Philippe

doi:10.1021/ja068720e

Cited by 136 publications

(181 citation statements)

References 98 publications

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“…However, as a big surprise these hydroxyl groups are Brønsted acidic in nature [9,23]. That is astonishing because we would normally expect the hydrolysis of an Mg-OCH 3 bond to result in a Brønsted basic Mg-OH group as is commonly known for magnesium hydroxide [20,21,24].…”

Section: Hydroxylated Metal Fluoridesmentioning

confidence: 94%

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

et al. 2010

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In this article, the high potential of the fluorolytic sol-gel process to synthesise nanoscopic metal fluorides with different acid-base properties is shown. These nanoscopic materials exhibit high potential to be used as heterogeneous catalysts due to their high surface areas and their tunable surface properties. Thus, for each specific reaction the required surface properties of the catalysts can be "adjusted" to achieve a high yield and selectivity of the desired product. As a consequence, a greener method of chemical production can be accomplished. Moreover the cheap and easy synthesis of the catalysts using basic chemicals makes them not only interesting for fundamental research but provides an easy transformation to industrial applications.

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Section: Hydroxylated Metal Fluoridesmentioning

confidence: 94%

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

et al. 2010

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“…[21] Thermal activation at 1173 K produces virtually hydroxy-free samples. [22,23] In the case of sodium, potassium, and rubidium, metal shots were distilled in a vacuum to form a metal mirror in a separate part of the quartz cell used for EPR measurements. The cesium metallic mirror was formed by the thermal decomposition of CsN 3 .…”

Section: Methodsmentioning

confidence: 99%

Properties of Alkali Metal Atoms Deposited on a MgO Surface: A Systematic Experimental and Theoretical Study

Finazzi

Valentin

Pacchioni

et al. 2008

Chemistry A European J

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The adsorption of small amounts of alkali metal atoms (Li, Na, K, Rb, and Cs) on the surface of MgO powders and thin films has been studied by means of EPR spectroscopy and DFT calculations. From a comparison of the measured and computed g values and hyperfine coupling constants (hfccs), a tentative assignment of the preferred adsorption sites is proposed. All atoms bind preferentially to surface oxide anions, but the location of these anions differs as a function of the deposition temperature and alkali metal. Lithium forms relatively strong bonds with MgO and can be stabilized at low temperatures on terrace sites. Potassium interacts very weakly with MgO and is stabilized only at specific sites, such as at reverse corners where it can interact simultaneously with three surface oxygen atoms (rubidium and cesium presumably behave in the same way). Sodium forms bonds of intermediate strength and could, in principle, populate more than a single site when deposited at room temperature. In all cases, large deviations of the hfccs from the gas-phase values are observed. These reductions in the hfccs are due to polarization effects and are not connected to ionization of the alkali metal, which would lead to the formation of an adsorbed cation and a trapped electron. In this respect, hydrogen atoms behave completely differently. Under similar conditions, they form (H(+))(e(-)) pairs. The reasons for this different behavior are discussed.

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“…The band at 3627 cm À1 has been assigned to a hydrogenbonded Mg À OH···O species, where O represents an adjacent surface oxygen atom. [58] At t = 300 s, a band due to adsorbed acetone was observed at 1700 cm…”

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confidence: 99%

Oxidant‐Free Dehydrogenation of Alcohols Heterogeneously Catalyzed by Cooperation of Silver Clusters and Acid–Base Sites on Alumina

Shimizu

Sugino

Sawabe

et al. 2009

Chemistry A European J

223

178

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A gamma-alumina-supported silver cluster catalyst--Ag/Al(2)O(3)--has been shown to act as an efficient heterogeneous catalyst for oxidant-free alcohol dehydrogenation to carbonyl compounds at 373 K. The catalyst shows higher activity than conventional heterogeneous catalysts based on platinum group metals (PGMs) and can be recycled. A systematic study on the influence of the particle size and oxidation state of silver species, combined with characterization by Ag K-edge XAFS (X-ray absorption fine structure) has established that silver clusters of sizes below 1 nm are responsible for the higher specific rate. The reaction mechanism has been investigated by kinetic studies (Hammett correlation, kinetic isotope effect) and by in situ FTIR (kinetic isotope effect for hydride elimination reaction from surface alkoxide species), and the following mechanism is proposed: 1) reaction between the alcohol and a basic OH group on the alumina to yield alkoxide on alumina and an adsorbed water molecule, 2) C-H activation of the alkoxide species by the silver cluster to form a silver hydride species and a carbonyl compound, and 3) H(2) desorption promoted by an acid site in the alumina. The proposed mechanism provides fundamental reasons for the higher activities of silver clusters on acid-base bifunctional support (Al(2)O(3)) than on basic (MgO and CeO(2)) and acidic to neutral (SiO(2)) ones. This example demonstrates that catalysts analogous to those based on of platinum group metals can be designed with use of a less expensive d(10) element--silver--through optimization of metal particle size and the acid-base natures of inorganic supports.

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Infrared Characterization of Hydroxyl Groups on MgO: A Periodic and Cluster Density Functional Theory Study

Cited by 136 publications

References 98 publications

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Properties of Alkali Metal Atoms Deposited on a MgO Surface: A Systematic Experimental and Theoretical Study

Oxidant‐Free Dehydrogenation of Alcohols Heterogeneously Catalyzed by Cooperation of Silver Clusters and Acid–Base Sites on Alumina

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