Earth-abundant Ni-Zn nanocrystals for efficient alkyne semihydrogenation catalysis.

The development of catalysts that are based on earth-abundant metals remains a grand challenge. Alloy nanocrystals (NCs) form an emerging class of heterogeneous catalysts, offering the promise of small, uniform catalysts with composition-control. Here, we report the synthesis of small Ni and bimetallic Ni-X (X= Zn, Ga, In) NCs for alkyne semihydrogenation catalysis.

H Quadrupolar Coupling Constant: A Spectroscopic Ruler for Transition Metal-Hydride Bond Distances in Molecular and Surface Sites.

Transition metal hydrides (TMHs) find numerous applications across fields from catalysis to H storage. Yet, determining the structure of TMHs can remain a challenge, as hydrogen is difficult to detect by X-ray based or classical spectroscopic techniques. Considering that the deuterium isotope (D) is a quadrupolar nucleus ( = 1) and that a quadrupolar coupling constant () depends on the distance between D and its bonding partner E (), we evaluate this trend across molecularly defined transition metal deuterides (TMDs) through a systematic investigation across TM block elements using both computations and experiments.

Conversion of Syngas to Ethanol over a RhFe Alloy Catalyst.

The direct conversion of syngas to ethanol is a promising route for the sustainable production of value-added chemicals and fuels. While Fe-promoted Rh-based catalysts have long been studied because of their notable activity and selectivity toward ethanol, the catalyst structure and the nature of Rh-Fe interaction remain poorly understood under reaction conditions, due to the intrinsic complexity of heterogeneous catalysts prepared by conventional approaches. In this work, we construct well-defined RhFe@SiO model catalysts via surface organometallic chemistry, composed of small and narrowly distributed nanoparticles supported on silica.

Contorted acene ribbons for stable and ultrasensitive neural probes.

Organic materials that conduct both electrons and ions are integral to implantable bioelectronics because of their conformable nature. There is a dearth of these materials that are highly sensitive to cations, which are the majority ions on the surface of neurons. This manuscript offers a solution using an extended ribbon structure that is defect-free, providing high electronic mobility along its fused backbone, while the edge structure of these ribbons promotes high ionic conductivity.

Gallium: A Universal Promoter Switching CO Methanation Catalysts to Produce Methanol.

Hydrogenation of CO to methanol is foreseen as a key step to close the carbon cycle. In this study, we show that introducing Ga into silica-supported nanoparticles based on group 8-9 transition noble metals (M = Ru, Os, Rh, and Ir - Ga@SiO) switches their reactivity from producing mostly methane (sel. > 97%) to producing methanol (>50% CHOH/DME sel.

Molten Metal Synthesis of Nanographenes.

This manuscript describes a simple and effective method to cyclodehydrogenate arenes using liquid alkali metals. Direct reaction between molten potassium and arenes forms 6-membered rings and zigzag edged structures within polyarenes. The approach is extended to integration of pyridinic nitrogen and 5-membered rings to arene structures and synthesis of larger, open-shell nanographenes.

Origin of Reactivity Trends of an Elusive Metathesis Intermediate from NMR Chemical Shift Analysis of Surrogate Analogues.

Olefin metathesis has become an efficient tool in synthetic organic chemistry to build carbon-carbon bonds, thanks to the development of Grubbs- and Schrock-type catalysts. Olefin coordination, a key and often rate-determining elementary step for d Schrock-type catalysts, has been rarely explored due to the lack of accessible relevant molecular analogues. Herein, we present a fully characterized surrogate of this key olefin-coordination intermediate, namely, a cationic d tungsten oxo-methylidene complex bearing two -heterocyclic carbene ligands─[WO(CH)Cl(IMes)](OTf) () (IMes = 1,3-dimesitylimidazole-2-ylidene, OTf-triflate counteranion), resulting in a trigonal bipyramidal (TBP) geometry, along with its neutral octahedral analogue [WO(CH)Cl(IMes)] ()─and an isostructural oxo-methylidyne derivative [WO(CH)Cl(IMes)] ().

Metadynamics simulations reveal alloying-dealloying processes for bimetallic PdGa nanoparticles under CO hydrogenation.

Supported bimetallic nanoparticles (NPs) often display improved catalytic performances (activity and/or selectivity). Yet, structure-activity relationships are difficult to derive due to the multitude of possible compositions, interfaces and alloys. This is notably true for bimetallic NPs used in the selective hydrogenation of CO to methanol, where the NPs respond dynamically to the chemical potential of the reactants and products.

Ag NMR chemical shift as a descriptor for Brønsted acidity from molecules to materials.

Molecular-level understanding of the acid/base properties of heterogeneous catalysts requires the development of selective spectroscopic probes to establish structure-activity relationships. In this work we show that substituting the surface protons in oxide supports by isolobal N-heterocyclic carbene (NHC) Ag cations and measuring their Ag nuclear magnetic resonance (NMR) signatures enables to probe the speciation and to evaluate the corresponding Brønsted acidity of the substituted OH surface sites. Specifically, a series of silver N-heterocyclic carbene (NHC) Ag(i) complexes of general formula [(NHC)AgX] are synthesized and characterized, showing that the Ag NMR chemical shift of the series correlates with the Brønsted acidity of the conjugate acid of X (, HX), thus establishing an acidity scale based on Ag NMR chemical shift.

Geometry and Local Environment of Surface Sites in Vanadium-Based Ziegler-Natta Catalysts from V Solid-State NMR Spectroscopy.

Since its emergence over 50 years ago, the structure of surface sites in Ziegler-Natta catalysts, which are responsible for a major fraction of the world's supply of polyethylene (PE) and polypropylene (PP), has remained elusive. This is in part due to the complexity of these systems that involve multiple synthetic steps and components, namely, the MgCl support, a transition-metal chloride, and several organic modifiers, known as donors, that are used prior and in some instances during the activation step with alkyl aluminum. Due to the favorable nuclear magnetic resonance (NMR) properties of V and its use in Ziegler-Natta catalysts, we utilize V solid-state NMR spectroscopy to investigate the structure of VOCl on MgCl(thf).

Combining Atomic Layer Deposition with Surface Organometallic Chemistry to Enhance Atomic-Scale Interactions and Improve the Activity and Selectivity of Cu-Zn/SiO Catalysts for the Hydrogenation of CO to Methanol.

The direct synthesis of methanol via the hydrogenation of CO, if performed efficiently and selectively, is potentially a powerful technology for CO mitigation. Here, we develop an active and selective Cu-Zn/SiO catalyst for the hydrogenation of CO by introducing copper and zinc onto dehydroxylated silica via surface organometallic chemistry and atomic layer deposition, respectively. At 230 °C and 25 bar, the optimized catalyst shows an intrinsic methanol formation rate of 4.

Group 10 Metal Allyl Amidinates: A Family of Readily Accessible and Stable Molecular Precursors to Generate Supported Nanoparticles.

The synthesis of well-defined materials as model systems for catalysis and related fields is an important pillar in the understanding of catalytic processes at a molecular level. Various approaches employing organometallic precursors have been developed and established to make monodispersed supported nanoparticles, nanocrystals, and films. Using rational design principles, a new family of precursors based on group 10 metals suitable for the generation of small and monodispersed nanoparticles on metal oxides has been developed.

Surface Redox Dynamics in Gold-Zinc CO Hydrogenation Catalysts.

Au-Zn catalysts have previously been shown to promote the hydrogenation of CO to methanol, but their active state is poorly understood. Here, silica-supported bimetallic Au-Zn alloys, prepared by surface organometallic chemistry (SOMC), are shown to be proficient catalysts for hydrogenation of CO to methanol. X-ray absorption spectroscopy (XAS), in conjunction with gas-switching experiments, is used to amplify subtle changes occurring at the surface of this tailored catalyst during reaction.

Selective Oxidation of Methane to Methanol over Au/H-MOR.

Selective oxidation of methane to methanol by dioxygen (O) is an appealing route for upgrading abundant methane resource and represents one of the most challenging reactions in chemistry due to the overwhelmingly higher reactivity of the product (methanol) versus the reactant (methane). Here, we report that gold nanoparticles dispersed on mordenite efficiently catalyze the selective oxidation of methane to methanol by molecular oxygen in aqueous medium in the presence of carbon monoxide. The methanol productivity reaches 1300 μmol g h or 280 mmol g h with 75% selectivity at 150 °C, outperforming most catalysts reported under comparable conditions.

The promotional role of Mn in CO hydrogenation over Rh-based catalysts from a surface organometallic chemistry approach.

Rh-based catalysts modified by transition metals have been intensively studied for CO hydrogenation due to their high activity. However, understanding the role of promoters at the molecular level remains challenging due to the ill-defined structure of heterogeneous catalysts. Here, we constructed well-defined RhMn@SiO and Rh@SiO model catalysts surface organometallic chemistry combined with thermolytic molecular precursor (SOMC/TMP) approach to rationalize the promotional effect of Mn in CO hydrogenation.

From ethene to propene (ETP) on tailored silica-alumina supports with isolated Ni(ii) sites: uncovering the importance of surface nickel aluminate sites and the carbon-pool mechanism.

Catalysts with well-defined isolated Ni(ii) surface sites have been prepared on three silica-based supports. The outer shells of the support were comprised either of an amorphous aluminosilicate or amorphous alumina (AlO ) layer - associated with a high and low density of strong Brønsted acid sites (BAS), respectively. When tested for ethene-to-propene conversion, Ni catalysts with a higher density of strong BAS demonstrate a higher initial activity and productivity to propene.

Correction to "Silica-Supported PdGa Nanoparticles: Metal Synergy for Highly Active and Selective CO-to-CHOH Hydrogenation".

[This corrects the article DOI: 10.1021/jacsau.1c00021.

Single-Site Iridium Picolinamide Catalyst Immobilized onto Silica for the Hydrogenation of CO and the Dehydrogenation of Formic Acid.

The development of an efficient heterogeneous catalyst for storing H into CO and releasing it from the produced formic acid, when needed, is a crucial target for overcoming some intrinsic criticalities of green hydrogen exploitation, such as high flammability, low density, and handling. Herein, we report an efficient heterogeneous catalyst for both reactions prepared by immobilizing a molecular iridium organometallic catalyst onto a high-surface mesoporous silica, through a sol-gel methodology. The presence of tailored single-metal catalytic sites, derived by a suitable choice of ligands with desired steric and electronic characteristics, in combination with optimized support features, makes the immobilized catalyst highly active.

Silica-Supported PdGa Nanoparticles: Metal Synergy for Highly Active and Selective CO-to-CHOH Hydrogenation.

The direct conversion of CO to CHOH represents an appealing strategy for the mitigation of anthropogenic CO emissions. Here, we report that small, narrowly distributed alloyed PdGa nanoparticles, prepared via surface organometallic chemistry from silica-supported Ga isolated sites, selectively catalyze the hydrogenation of CO to CHOH. At 230 °C and 25 bar, high activity (22.

Heterogeneous alkane dehydrogenation catalysts investigated a surface organometallic chemistry approach.

The selective conversion of light alkanes (C2-C6 saturated hydrocarbons) to the corresponding alkene is an appealing strategy for the petrochemical industry in view of the availability of these feedstocks, in particular with the emergence of Shale gas. Here, we present a review of model dehydrogenation catalysts of light alkanes prepared via surface organometallic chemistry (SOMC). A specific focus of this review is the use of molecular strategies for the deconvolution of complex heterogeneous materials that are proficient in enabling dehydrogenation reactions.

Deciphering Metal-Oxide and Metal-Metal Interplay via Surface Organometallic Chemistry: A Case Study with CO Hydrogenation to Methanol.

Processes that rely on heterogeneous catalysts underpin the production of bulk chemicals and fuels. In spite of this, understanding of the interplay between the structure and reactivity of these complex materials remains elusive-rendering rational improvement of existing systems challenging. Herein, we describe efforts to understand complex materials capable of selective thermochemical conversion of CO to methanol using a surface organometallic chemistry (SOMC) approach.

Selective and catalytic carbon dioxide and heteroallene activation mediated by cerium N-heterocyclic carbene complexes.

A series of rare earth complexes of the form Ln(L) supported by bidentate -aryloxide-NHC ligands are reported (L = 2-O-3,5-Bu-CH(1-C{N(CH)N(R)})); R = Pr, Bu, Mes; Ln = Ce, Sm, Eu). The cerium complexes cleanly and quantitatively insert carbon dioxide exclusively into all three cerium carbene bonds, forming Ce(L·CO). The insertion is reversible only for the mesityl-substituted complex Ce(L).