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Apart from large surface areas, low activation energies are essential for efficient reactions, particularly in heterogeneous catalysis. Here, we show that not only the size of nanoparticles but also their detailed morphology can crucially affect reaction kinetics, as demonstrated for mass-selected, soft-landed, and oxidized cobalt clusters in a 6 nm to 18 nm size range. The method of reflection high-energy electron diffraction is extended to the quantitative determination of particle activation energies which is applied for repeated oxidation and reduction cycles at the same particles. We find unexpectedly small activation barriers for the reduction reaction of the largest particles studied, despite generally increasing barriers for growing sizes. We attribute these observations to the interplay of reactionspecific material transport with a size-dependent inner particle morphology. [ABSTRACT FROM AUTHOR]

The article explores the detection of single nanoparticle activity dynamics inside a model pore catalyst material. It mentions the results of a study reveal a general framework for single particle catalysis in the gas phase and highlight the importance of single particle approaches for the understanding of complex catalyst materials.

[Display omitted] • A series of Fe-based catalysts differing in surface Na/Fe ratio were prepared. • The critical role of Na is beyond its promotional effects under stationary operation. • Surface Na/Fe ratio determines the response of performance to fluctuating conditions. • Catalyst dynamics induced by fluctuating reaction conditions were studied. • The effect of Na in securing iron carbides was studied by in situ characterization. Considering the on-going developments of approaches for CO 2 capture, storage, and utilization, CO 2 hydrogenation with renewable H 2 can become sustainable technology to produce value-added chemicals/fuels in future feedstock scenarios. Herein, we investigate temporal behaviors of Fe-based catalysts in CO 2 hydrogenation under externally forced dynamics of reactor operation from the respective of composition and performance. Different catalyst preparation methods were applied to modulate the surface concentration of Na promoter but keeping the bulk concentration constant. The crucial promoter role in reserving catalyst performance and (un)steady-state catalyst composition during dynamic reactor operation was investigated by means of sophisticated catalytic tests combined with in situ and ex situ catalyst characterizations. The surface Na/Fe ratio of spent catalysts was identified as the decisive descriptor for production of the desired products under dynamic CO 2 hydrogenation conditions. The derived knowledge could be useful for redesigning catalysts and optimizing reaction processes when employing fluctuating energy supply. [ABSTRACT FROM AUTHOR]

The synthesis of primary alcohols (from olefins) is an important and challenging transformation, as most of the current methods suffer from regioselectivity issues. This work describes the utilization of rice husk (RH) from agricultural waste as support for the preparation of a catalyst for the conversion of olefin oxides to primary alcohols. The catalyst was synthesized by pyrolysis of RH impregnated with nickel, and characterized by IR, AAS, XRD, BET, XPS, TEM, and TPD technics. The catalyst shows excellent activity and selectivity towards anti‐Markovnikov alcohols, acting simultaneously as Brønsted acid, solid Lewis acid, and as hydrogenation catalyst. A substrate screening was done, the catalyst's recycling stability was assessed, and a plausibly reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

Earth abundant metal‐based heterogeneous catalysts with highly active and at the same time stable isolated metal sites constitute a key factor for the advancement of sustainable and cost‐effective chemical synthesis. In particular, the development of more practical, and durable iron‐based materials is of central interest for organic synthesis, especially for the preparation of chemical products related to life science applications. Here, we report the preparation of Fe‐single atom catalysts (Fe‐SACs) entrapped in N‐doped mesoporous carbon support with unprecedented potential in the preparation of different kinds of amines, which represent privileged class of organic compounds and find increasing application in daily life. The optimal Fe‐SACs allow for the reductive amination of a broad range of aldehydes and ketones with ammonia and amines to produce diverse primary, secondary, and tertiary amines including N‐methylated products as well as drugs, agrochemicals, and other biomolecules (amino acid esters and amides) utilizing green hydrogen. [ABSTRACT FROM AUTHOR]

Earth abundant metal‐based heterogeneous catalysts with highly active and at the same time stable isolated metal sites constitute a key factor for the advancement of sustainable and cost‐effective chemical synthesis. In particular, the development of more practical, and durable iron‐based materials is of central interest for organic synthesis, especially for the preparation of chemical products related to life science applications. Here, we report the preparation of Fe‐single atom catalysts (Fe‐SACs) entrapped in N‐doped mesoporous carbon support with unprecedented potential in the preparation of different kinds of amines, which represent privileged class of organic compounds and find increasing application in daily life. The optimal Fe‐SACs allow for the reductive amination of a broad range of aldehydes and ketones with ammonia and amines to produce diverse primary, secondary, and tertiary amines including N‐methylated products as well as drugs, agrochemicals, and other biomolecules (amino acid esters and amides) utilizing green hydrogen. [ABSTRACT FROM AUTHOR]

The development of highly efficient and stable visible-light-driven photocatalysts for the removal of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water is still a challenge. In this work, Bi2MoO6 (BMO) materials with different morphology were successfully prepared via a simple hydrothermal method by altering the solvent. The morphology of the BMO material is mainly influenced by the solvent used in the synthesis (H2O, ethanol, and ethylene glycol or their mixtures) and to a lesser extent by subsequent thermal annealing. BMO with aggregated spheres and nanoplate-like structures hydrothermally synthesized in ethylene glycol (EG) and subsequently calcined at 400 °C (BMO-400 (EG)) showed the highest adsorption capacity and photocatalytic activity compared to other synthesized morphologies. Complete degradation of 2,4-D on BMO upon irradiation with a blue light-emitting diode (LED, λmax = 467 nm) was reached within 150 min, resulting in 2,4-dichlorophenol (2,4-DCP) as the main degradation product. Holes (h+) and superoxide radicals (⋅O2−) are assumed to be the reactive species observed for the rapid conversion of 2,4-D to 2,4-DCP. The addition of H2O2 to the reaction mixture not only accelerates the degradation of 2,4-DCP but also significantly reduces the total organic carbon (TOC) content, indicating that hydroxyl radicals are crucial for the rapid mineralization of 2,4-D. Under optimal conditions, the TOC value was reduced by 84.5% within 180 min using BMO-400 (EG) and H2O2. The improved degradation performance of BMO-400 (EG) can be attributed to its particular morphology leading to lower charge transfer resistance, higher electron–hole separation, and larger specific surface area. [ABSTRACT FROM AUTHOR]

There is a constant need for deuterium‐labelled products for multiple applications in life sciences and beyond. Here, a new class of heterogeneous catalysts is reported for practical deuterium incorporation in anilines, phenols, and heterocyclic substrates. The optimal material can be conveniently synthesised and allows for high deuterium incorporation using deuterium oxide as isotope source. This new catalyst has been fully characterised and successfully applied to the labelling of natural products as well as marketed drugs. [ABSTRACT FROM AUTHOR]

There is a constant need for deuterium‐labelled products for multiple applications in life sciences and beyond. Here, a new class of heterogeneous catalysts is reported for practical deuterium incorporation in anilines, phenols, and heterocyclic substrates. The optimal material can be conveniently synthesised and allows for high deuterium incorporation using deuterium oxide as isotope source. This new catalyst has been fully characterised and successfully applied to the labelling of natural products as well as marketed drugs. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride (p-C 3 N 4) based materials have shown great potential as photocatalysts for degradation of pollutants from wastewater. In this work p-C 3 N 4 was synthesized from urea or ferric chloride/urea by pyrolysis followed by a post-treatment with hydrogen peroxide (H 2 O 2). The prepared materials were characterized by physico-chemical methods in order to study their structural and electronic features. The characterization results revealed that iron was present in p-C 3 N 4 as a Fe 3 O 4 phase. The H 2 O 2 treatment did not only modify the p-C 3 N 4 framework through the generation of oxygen functional groups and defect sites but it also affected the size, distribution, and oxidation state of iron oxide. The photocatalytic activity of the catalysts was tested through the degradation of methyl orange under visible and white light irradiation. In comparison, the iron oxide containing p-C 3 N 4 post-treated with H 2 O 2 sample shows superior photocatalytic performance towards methyl orange degradation. This might be attributed to the valence and conduction band levels of the composite material, an inhibited recombination of photogenerated charge carriers as well as a synergistic effect of iron species and the oxygen containing functional groups or defects present in p-C 3 N 4. [ABSTRACT FROM AUTHOR]

The nature of the support can fundamentally affect the function of a heterogeneous catalyst. For the novel type of isolated metal atom catalysts, sometimes referred to as single‐atom catalysts, systematic correlations are still rare. Here, we report a general finding that Pd on nitride supports (non‐metal and metal nitride) features a higher oxidation state compared to that on oxide supports (non‐metal and metal oxide). Through thorough oxidation state investigations by X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), CO‐DRIFTS, and density functional theory (DFT) coupled with Bader charge analysis, it is found that Pd atoms prefer to interact with surface hydroxyl group to form a Pd(OH)x species on oxide supports, while on nitride supports, Pd atoms incorporate into the surface structure in the form of Pd−N bonds. Moreover, a correlation was built between the formal oxidation state and computational Bader charge, based on the periodic trend in electronegativity. [ABSTRACT FROM AUTHOR]

The nature of the support can fundamentally affect the function of a heterogeneous catalyst. For the novel type of isolated metal atom catalysts, sometimes referred to as single‐atom catalysts, systematic correlations are still rare. Here, we report a general finding that Pd on nitride supports (non‐metal and metal nitride) features a higher oxidation state compared to that on oxide supports (non‐metal and metal oxide). Through thorough oxidation state investigations by X‐ray absorption spectroscopy (XAS), X‐ray photoelectron spectroscopy (XPS), CO‐DRIFTS, and density functional theory (DFT) coupled with Bader charge analysis, it is found that Pd atoms prefer to interact with surface hydroxyl group to form a Pd(OH)x species on oxide supports, while on nitride supports, Pd atoms incorporate into the surface structure in the form of Pd−N bonds. Moreover, a correlation was built between the formal oxidation state and computational Bader charge, based on the periodic trend in electronegativity. [ABSTRACT FROM AUTHOR]

Improving the selectivity in the oxidative coupling of methane to ethane/ethylene poses a significant challenge for commercialization. The required improvements are hampered by the uncertainties associated with the reaction mechanism due to its complexity. Herein, we report about 90 % selectivity to the target products at 11 % methane conversion over Gd2O3‐based catalysts at 700 °C using N2O as the oxidant. Sophisticated kinetic studies have suggested the nature of adsorbed oxygen species and their binding strength as key parameters for undesired methane oxidation to carbon oxides. These descriptors can be controlled by a metal oxide promoter for Gd2O3. [ABSTRACT FROM AUTHOR]

Improving the selectivity in the oxidative coupling of methane to ethane/ethylene poses a significant challenge for commercialization. The required improvements are hampered by the uncertainties associated with the reaction mechanism due to its complexity. Herein, we report about 90 % selectivity to the target products at 11 % methane conversion over Gd2O3‐based catalysts at 700 °C using N2O as the oxidant. Sophisticated kinetic studies have suggested the nature of adsorbed oxygen species and their binding strength as key parameters for undesired methane oxidation to carbon oxides. These descriptors can be controlled by a metal oxide promoter for Gd2O3. [ABSTRACT FROM AUTHOR]

Preferential CO Oxidation in H 2 -rich streams is a promising approach to decrease CO concentrations below 10 ppm for fuel cell applications. Herein, Cu catalysts supported on commercial CeO 2 are prepared by a simple ball-milling method with different Cu loadings (0.25, 0.5, and 1 wt%). The catalysts are characterized by various methods, including XRD, BET, STEM-EELS, and H 2 -TPR. The results show that the catalysts are highly active and selective during CO-PROX in 80 vol% H 2 -streams at different temperatures. Moreover, all catalysts exhibited high stability and 100 % CO 2 -selectivity throughout 75 h of reaction at 90 °C. However, increasing Cu loading caused a decrease in Cu-mass-normalized rate due to the formation of less active CuO x clusters. The combined results from operando DRIFTS, EPR and NAP-XPS reveal that single Cu atom sites on CeO 2 are the key factor for the enhanced catalytic performance while the decreased activity is due to CuO x cluster formation. • Supported Cu-single sites on commercial CeO 2 - are highly active and selective for CO-PRX reaction. • Cu/CeO 2 catalysts prepared by simple ball-milling method. • No appreciable deactivation during 75 h on stream with 100 % selectivity at 90 °C. • CuO x cluster/nanoparticles are less active for CO-PROX. • Cu2+−O–Ce4+ and Cu+−□−Ce3+ moieties are the active sites for CO-PROX. [ABSTRACT FROM AUTHOR]

A protocol for efficient N-alkylation of benzamides with alcohols in the presence of cobalt-nanocatalysts is described. Key to the success of this general methodology is the use of highly dispersed cobalt nanoparticles supported on carbon, which are obtained from the pyrolysis of cobalt(II) acetate and o-phenylenediamine as a ligand at suitable temperatures. The catalytic material shows a broad substrate scope and good tolerance to functional groups. Apart from the synthesis of a variety of secondary amides (>45 products), the catalyst allows for the conversion of more challenging aliphatic alcohols and amides, including biobased and macromolecular amides. The practical applicability of the catalyst is underlined by the successful recycling and reusability. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation and oxidative dehydrogenation of N‐heterocycles to produce tetrahydroquinoline and quinoline derivatives are important reactions of particular importance in the agrochemical and pharmaceutical industries. Herein, we report earth‐abundant cobalt nanoparticles supported on hydroxyapatite (HAP) as an inexpensive and efficient catalyst for the hydrogenation and reverse oxidative dehydrogenation of N‐heterocycles. The optimal nanocatalyst exhibits excellent activity in both reactions for a wide range of substrates including (iso)quinolines, acridine, benzo[h]quinoline, quinoxaline and indole. Reactions proceed under relatively mild conditions without requiring any additives. [ABSTRACT FROM AUTHOR]

A setup for dispersive X-ray absorption spectroscopy (XAS) with spatial, temporal and energy resolution is presented. Through investigation of a Mo/HZSM-5 catalyst during the dehydroaromatization of methane we observed a reduction gradient along the packed bed. Our new method represents an unprecedented addition to the analytical toolbox for in situ characterizations. [ABSTRACT FROM AUTHOR]

Heterogeneously catalyzed N‐formylation of amines to formamide with CO2/H2 is highly attractive for the valorization of CO2. However, the relationship of the catalytic performance with the catalyst structure is still elusive. Herein, mixed valence catalysts containing Cu2O/Cu interface sites were constructed for this transformation. Both aliphatic primary and secondary amines with diverse structures were efficiently converted into the desired formamides with good to excellent yields. Combined ex and in situ catalyst characterization revealed that the presence of Cu2O/Cu interface sites was vital for the excellent catalytic activity. Density functional theory (DFT) calculations demonstrated that better catalytic activity of Cu2O/Cu(111) than Cu(111) is attributed to the assistance of oxygen at the Cu2O/Cu interface (Ointer) in formation of Ointer‐H moieties, which not only reduce the apparent barrier of HCOOH formation but also benefit the desorption of the desired N‐formylated amine, leading to high activity and selectivity. [ABSTRACT FROM AUTHOR]

Heterogeneously catalyzed N‐formylation of amines to formamide with CO2/H2 is highly attractive for the valorization of CO2. However, the relationship of the catalytic performance with the catalyst structure is still elusive. Herein, mixed valence catalysts containing Cu2O/Cu interface sites were constructed for this transformation. Both aliphatic primary and secondary amines with diverse structures were efficiently converted into the desired formamides with good to excellent yields. Combined ex and in situ catalyst characterization revealed that the presence of Cu2O/Cu interface sites was vital for the excellent catalytic activity. Density functional theory (DFT) calculations demonstrated that better catalytic activity of Cu2O/Cu(111) than Cu(111) is attributed to the assistance of oxygen at the Cu2O/Cu interface (Ointer) in formation of Ointer‐H moieties, which not only reduce the apparent barrier of HCOOH formation but also benefit the desorption of the desired N‐formylated amine, leading to high activity and selectivity. [ABSTRACT FROM AUTHOR]

The selective hydrogenation of benzofurans in the presence of a heterogeneous non‐noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt‐cobalt oxide core–shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt‐DABCO‐citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3‐dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co‐nanocatalyst are demonstrated. [ABSTRACT FROM AUTHOR]

The selective hydrogenation of benzofurans in the presence of a heterogeneous non‐noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt‐cobalt oxide core–shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt‐DABCO‐citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3‐dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co‐nanocatalyst are demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] Lateral adhesion forces are a fundamental property of liquid–solid interactions and a key aspect of dynamic droplet mobility. But, commonly applied conventional wetting analysis is limited to static and quasi-static methods and cannot resolve dynamic and spatial liquid–solid interactions. However, droplet mobility is assumed to be affected by chemical and topographic surface inhomogeneities introduced by femtosecond laser treatment. In this study, we used a customized droplet adhesion force instrument to determine lateral adhesion forces on various femtosecond laser-structured surface designs to obtain a deeper understanding of the dynamic droplet motion with regard to chemical and topographic surface features. We show that the droplet motion was highly affected by the chemical and topographical surface design and local inhomogeneities. The droplet mobility on femtosecond laser-structured surfaces could be classified into a static, a transfer, and a kinetic regime, which is essential for designing surfaces with extreme wetting characteristics and a wide range of scientific and industrial processes. Furthermore, with proper tailoring of surface structures and chemical modification, we were able to provoke adhesion forces on self-organized laser microstructures similar to those found on the natural lotus leaves. [ABSTRACT FROM AUTHOR]

[Display omitted] Lateral adhesion forces are a fundamental property of liquid–solid interactions and a key aspect of dynamic droplet mobility. But, commonly applied conventional wetting analysis is limited to static and quasi-static methods and cannot resolve dynamic and spatial liquid–solid interactions. However, droplet mobility is assumed to be affected by chemical and topographic surface inhomogeneities introduced by femtosecond laser treatment. In this study, we used a customized droplet adhesion force instrument to determine lateral adhesion forces on various femtosecond laser-structured surface designs to obtain a deeper understanding of the dynamic droplet motion with regard to chemical and topographic surface features. We show that the droplet motion was highly affected by the chemical and topographical surface design and local inhomogeneities. The droplet mobility on femtosecond laser-structured surfaces could be classified into a static, a transfer, and a kinetic regime, which is essential for designing surfaces with extreme wetting characteristics and a wide range of scientific and industrial processes. Furthermore, with proper tailoring of surface structures and chemical modification, we were able to provoke adhesion forces on self-organized laser microstructures similar to those found on the natural lotus leaves. [ABSTRACT FROM AUTHOR]

Correction for 'Time-, space- and energy-resolved in situ characterization of catalysts by X-ray absorption spectroscopy' by Stefan Peters et al., Chem. Commun., 2023, 59, 12120–12123, https://doi.org/10.1039/D3CC03277A. [ABSTRACT FROM AUTHOR]

A heterogeneous single‐atom catalyst (SAC) based on a tiny Cu loading (0.05 wt.%) supported on CeO2−TiO2 (Ce/Ti=0.18) shows very high Cu mass‐normalized CO oxidation activity, 100 % selectivity for CO2 between 60 and 100 °C and essentially no deactivation during 17 h on stream in the preferential oxidation of CO (PROX) at 120 °C. Based on state of the art, this catalyst is among the most active and PROX‐selective catalysts. Employing a combination of ex‐situ and operando methods, we infer that the isolated Cu single sites are incorporated with redox‐active Cu2+−O−Ce4+⇆Cu+−□−Ce3+ moieties connected by labile oxygen and are exposed on the surface of highly dispersed ceria. This high dispersion is promoted by TiO2 which itself does not participate in redox steps during PROX, as Ti ions remain essentially tetravalent while Cu and Ce undergo reversible redox shuttles. [ABSTRACT FROM AUTHOR]

The synthesis of vitamin precursors via alkyne semi-hydrogenation has been achieved with a lead- and palladium-free catalyst. Cobalt nanoparticles modified by nitrogen doped carbon and supported on silica allow the production of a range of fine chemicals and vitamin precursors. The optimal catalyst could be conveniently recycled and used for at least five runs with consistent activity. Interestingly, this material selectively hydrogenates alkynes in the presence of easily reducible, cyano-, keto-, aldehyde-, and even nitro groups, which shows it to be a versatile catalyst for synthetic organic chemistry. [ABSTRACT FROM AUTHOR]

A convenient and practical diastereoselective cis-hydrogenation of multi-substituted pyridines and arenes is reported. Applying a novel heterogeneous ruthenium catalyst, the corresponding piperidines and cyclohexanes are obtained in high yields (typically >80%) with a good functional group tolerance under mild conditions. The robust ruthenium supported catalyst is smoothly prepared and can be reused multiple times without activity loss. [ABSTRACT FROM AUTHOR]

We communicate the assembly of a solid, Ce-promoted Ni-based composite that was applied as catalyst for the hydrogenation of nitroarenes to afford the corresponding organic amines. The catalytically active material described herein was obtained through pyrolysis of a SiO2-pellet-supported bimetallic Ni-Ce complex that was readily synthesized prior to use from a MeO-functionalized salen congener, Ni(OAc)2·4 H2O, and Ce(NO3)3·6 H2O. Rewardingly, the requisite ligand for the pertinent solution phase precursor was accessible upon straightforward and time-saving imine condensation of ortho-vanillin with 1,3-diamino-2,2′-dimethylpropane. The introduced catalytic protocol is operationally simple in that the whole reaction set-up is quickly put together on the bench without the need of cumbersome handling in a glovebox or related containment systems. Moreover, the advantageous geometry and compact-sized nature of the used pellets renders the catalyst separation and recycling exceptionally easy. [ABSTRACT FROM AUTHOR]

A general heterogeneous cobalt-catalysed CH-alkylation of indoles with alcohols is reported. Utilizing this straightforward borrowing hydrogen methodology, a series of substituted and functionalized indoles were easily coupled with benzylic, heterocyclic, and aliphatic alcohols including methanol to prepare >65 substituted indoles in good to excellent yields. The resulting products represent an interesting class of heterocyclic compounds widely used in organic synthesis and medicinal chemistry. Key for this synthesis is the use of specific cobalt-nanoparticles supported on N-doped carbon, which were conveniently prepared by the pyrolysis of a templated material generated in situ by mixing cobalt-nitrate, zinc-nitrate, 2,6-diaminopyridine, and colloidal silica, and subsequent removal of silica. [ABSTRACT FROM AUTHOR]

CO 2 conversion to CO via the reverse water-gas shift (RWGS) reaction is a promising source of syngas for subsequent synthesis of liquid fuels and chemicals. Herein, we present the synthesis of catalysts containing Au supported on hydroxylated Na-modified ZrO 2 , with Au amounts ranging from 0.05 to 1 wt%. Systematic investigations reveal the formation of cooperative Au/Na sites at the interface. These sites cooperate synergistically to activate CO 2 and generate a high surface density of carboxylate-like species, which serve as highly active intermediates for CO formation. It was found that the RWGS reaction on the catalyst with low Au loading proceeds mainly via a carboxylate pathway, with bidentate formate acting as spectators. At higher Au loading, the bidentate formate pathway contributes somewhat to CO formation alongside the carboxylate pathway. Based on temporal analysis of products, we emphasize the significant roles of H 2 spillover and the metal-support interface in the RWGS reaction. [Display omitted] • ZrO2 prepared at high pH with NaOH contains strongly adsorbed surface Na species. • Hydroxylated Na-modified ZrO2 is an excellent support for gold catalysts for RWGS. • Surface Au and Na sites synergistically activate CO2 and boosting CO formation. • In-situ spectroscopic studies reveal carboxylate as active intermediates for RWGS. [ABSTRACT FROM AUTHOR]

This document is a summary of an article titled "Titelbild: Fundamentals of Unanticipated Efficiency of Gd2O3-based Catalysts in Oxidative Coupling of Methane (Angew. Chem. 14/2024)" published in the journal Angewandte Chemie. The article discusses the role of adsorbed oxygen species in determining the product selectivity in the oxidative coupling of methane. The authors, Guiyuan Jiang, Evgenii V. Kondratenko, and others, describe how the binding strength of selective mono-atomic oxygen species affects the formation of carbon oxides and ethane, which in turn affects the recombination probability of diatomic oxygen species. The article also briefly mentions other research topics such as the utilization of nanographenes as carriers of fluorophores, site-selective photocrosslinking of DNA duplex, and a rapid functional group transformation method using a reagent called 4-nitrophenyl-2H-azirine. [Extracted from the article]

This document is a summary of an article titled "Cover Picture: Fundamentals of Unanticipated Efficiency of Gd2O3-based Catalysts in Oxidative Coupling of Methane" published in the journal Angewandte Chemie International Edition. The article discusses how the selectivity of products in the oxidative coupling of methane is determined by the nature of adsorbed oxygen species. The authors describe how the binding strength of selective mono-atomic oxygen species affects the formation of carbon oxides and ethane, which in turn affects the probability of their recombination to diatomic oxygen species that oxidize methane to carbon oxides. The article also briefly mentions other research topics such as the utilization of nanographenes as carriers of fluorophores, site-selective photocrosslinking of DNA duplex, and a rapid functional group transformation method using a specific reagent. [Extracted from the article]

[Display omitted] • Co/ZrO 2 catalysts with single Co2+ are efficient for C 3 H 8 dehydrogenation to C 3 H 6. • 1Co/ZrO 2 performed durable over multiple dehydrogenation/regeneration cycles. • 1Co/ZrO 2 showed higher activity than a commercial analogue of K-CrO x /Al 2 O 3. • The high activity results from a synergy effect between Co2+ and Zr cus. • Recombination of surface H species is the rate-limiting step in C 3 H 6 formation. Due to the increased production of shale gas containing propane, the share of non-oxidative propane dehydrogenation (PDH) in the large-scale production of propene is expected to continue to grow. There are, however, some ecofriendly and cost shortcomings associated with the currently applied Cr- or Pt-containing catalysts. Against this background, we present here Co/ZrO 2 alternatives and reveal the fundamentals affecting their activity, which can be used for purposeful catalyst design. Co2+ species homogeneously distributed within the lattice of ZrO 2 significantly increase the activity of coordinatively unsaturated Zr4+ for the PDH reaction. The increase is caused by accelerating both the cleavage of CH bonds in propane and the recombination of surface H species, with the latter reaction being the rate-limiting step. The best-performing catalyst outperformed an analogue of commercial K-CrO x /Al 2 O 3 in terms of the rate of propene formation and demonstrated durable performance over a series of 10 PDH/regeneration cycles under industrially relevant conditions. It also outperformed most previously developed Co-containing catalysts in terms of propene productivity. The space–time yield of propene formation achieved at 57 % equilibrium propane conversion at 550 °C was 0.71 kg·h−1·kg cat -1. [ABSTRACT FROM AUTHOR]

[Display omitted] • The formation of self-organized structures depends on the laser scanning strategy. • A high scanning pulse overlap leads to dominating vapor–liquid solid growth. • A high scanning line overlap leads primarily to preferential valley ablation. • Scanning strategy affects crystallinity & chemical composition of microstructures. • Fs-laser treatment can lead to a significant heat-affected-zone (HAZ). This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti 3 Al), sub-oxides and oxides (Ti 6 O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material. [ABSTRACT FROM AUTHOR]

Using cheap and non-toxic chelating agents during catalyst preparation is considered as an effective tool to control the particle size and to strengthen the metal-support interactions (MSI), while keeping the simplicity of the selected preparation method. The previous properties are useful to improve the catalyst activity, stability, and selectivity in dry reforming of methane (DRM). Therefore, we prepared a series of low Ni loading (2.5 wt%) catalysts supported over MgO-Al 2 O 3 (Mg/Al = 1.3) mixed oxide using the classic wet impregnation method modified with chelating agents (citric acid (CA), tartaric acid (TA) and diethylenetriaminepentaacetic acid (DTPA)) and subsequently evaluated these in DRM. Intensive catalyst characterization (ICP, BET, XRD, XPS, STEM, H 2 -TPR and O 2 -TPO) suggested the presence of different structure-activity relationships. Particularly, using chelating agents during catalyst preparation controlled the final particle size range, which in turn played a pivotal role in shaping the strength of the metal support interactions (MSI). These impacts were crucial to improve the activity, stability and to control the formation of coke deposits. Moreover, special focus was put on the catalytic testing of the outperforming sample (Ni(TA)/Mg 1.3 AlO x) prepared using tartaric acid as chelating agent under severe regimes prone to catalyst deactivation to demonstrate the benefits of the proposed preparation technique. [Display omitted] • Organic ligands affect Ni particle size and its metal-support interaction (MSI). • Adding tartaric acid (TA) during preparation gave the best catalyst. • Up to 60% less coking at high GHSV and excess CH 4. • Ni(TA)/Mg 1.3 AlO x lost only 10% conversion at 600 °C over 50 h runtime. • Ni reoxidation and coke deposition are the main reasons of catalyst deactivation. [ABSTRACT FROM AUTHOR]

The effect of chemical solvents on the wetting state of laser-structured surfaces over time is systematically examined in this paper. By using a 300-fs laser, nanostructures were generated on Ti6Al4V, subsequently cleaned in an ultrasonic bath with different solvents and stored in ambient air. The static contact angle showed significant differences for cleaning with various solvents, which, depending on the applied cleaning and time, amounted up to 100°. X-ray photoelectron spectroscopy analyses reveal that the cleaning of the laser-structured surfaces affects the surface chemistry and the aging behavior of the surfaces, even with highly volatile solvents. The effect of the chemical surface modification is particularly noticeable when using alcohols for cleaning, which, due to their OH groups, cause highly hydrophilic behavior of the surface after one day of storage. Over the course of 14 days, enrichment with organic groups from the atmosphere occurs on the surface, which leads to poorer wetting on almost every structured surface. In contrast, the cleaning in hexane leads to a fast saturation of the surface with long-chain carbon groups and thus to a time-independent hydrophobic behavior. [ABSTRACT FROM AUTHOR]

Highly active and coking‐resistant Ni catalysts suited for the dry reforming of CH4‐rich gases (70 vol %, e. g. biogas or sour natural gas) were prepared starting from a Mg‐rich Mg−Al hydrotalcite support precursor. Calcination at 1000 °C yields two phases, MgO and MgAl2O4 spinel. Complexation‐deposition of Ni with citric acid on the preformed support as well as lanthanum addition yields a catalyst with remarkably low carbon accumulation over 100 h on stream attributed to both high Ni dispersion and preferred interactions of Ni with MgO on MgAl2O4. [ABSTRACT FROM AUTHOR]

• MgO incorporation in ZrO 2 boosts CO 2 methanation activity of Ru/ZrO 2. • The concentration of O-vacancies modulates the stability of intermediates. • Different electronic/adsorptive properties proved by in-situ DRIFT and EPR investigations. O-vacancies are defects commonly correlated with the production of CH 4 by CO 2 hydrogenation on reducible catalysts. Their effect on the stability of active CO ads and its origin is, however, not commonly explored for low Ru-loaded catalysts (Ru < 0.5 wt%). Herein, we investigated two catalysts containing a comparable amount of Ru (≈ 0.4 wt%) on two different zirconia supports: ZrO 2 and ZrO 2 -MgO (2.6 wt%-MgO). The rate of CH 4 formation on Ru/ZrO 2 -MgO is ca. 3-fold higher than on Ru/ZrO 2. Combined results from various ex-situ and in-situ characterization techniques provide evidence supporting the correlation between methane evolution and the extended Ru-support perimeter as well as with changes in the bond strength of intermediates modulated by O-vacancies. This latter effect represents the main difference between the two catalysts since the replacement of Zr4+ by Mg2+ ions in the ZrO 2 lattice promotes the generation of O-vacancies, facilitating electron transfer from them to interfacial Ru sites. This not only enhances H 2 activation but also weakens the stability of adsorbed bidentate formate (b-HCOO- ads), which subsequently decomposes to CO ads and then hydrogenates to CH 4 at the Ru-support perimeter. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of olefins using noble metal catalysts or pyrophoric RANEY® nickel is of high importance in the chemical industry. From the point of view of green and sustainable chemistry, design and development of Earth-abundant, less toxic, and more environmentally friendly catalysts are highly desirable. Herein, we report the convenient preparation of active cobalt catalysts and their application in hydrogenations of a wide range of terminal and internal carbon–carbon double bonds in water under mild conditions. Catalysts are prepared on multi-gram scale by pyrolysis of cobalt acetate and uracil, guanine, adenine or L -tryptophan. The most active material Co-Ura/C-600 showed good productivity in industrially relevant hydrogenation of diisobutene to isooctane and in natural oil hardening. [ABSTRACT FROM AUTHOR]

For the first time, the oxidative dehydrogenation of (−)‐menthol to (−)‐menthone and (+)‐isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO2, CuO distributed on a basic support and RuMnCe/CeO2, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag‐based catalyst was 58 % at 64 % selectivity, with a Cu‐based catalyst 41 % at 51 % selectivity and with a Ru‐based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized. [ABSTRACT FROM AUTHOR]

Hydroformylation of olefins has been studied in the presence of specific heterogeneous cobalt nanoparticles. The catalytic materials were prepared by pyrolysis of preformed cobalt complexes deposited onto different inorganic supports. Atomic absorption spectroscopy (AAS) measurements indicated a correlation of catalyst activity and cobalt leaching as well as a strong influence of the heterogeneous support on the productivity. These new, low‐cost, easy‐to‐handle catalysts can substitute more toxic, unstable and volatile cobalt carbonyl complexes for hydroformylations on a laboratory scale. Co catalysis: A new class of low‐cost, easy‐to‐handle materials for lab‐scale hydroformylation is reported. The pyrolysis of preformed Co complexes deposited onto inorganic supports resulted in immobilised cobalt nanoparticles for oxo synthesis. The most active materials Co/phen@TiO2 and Co/phen@C represent convenient reservoirs for active homogeneous cobalt species, and thus can substitute the common, but toxic, dicobaltoctacarbonyl complex. [ABSTRACT FROM AUTHOR]

Abstract: A combined experimental and theoretical investigation of Ag‐Pt sub‐nanometer clusters as heterogeneous catalysts in the CO→CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size‐selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first‐principles simulations at realistic coverage. In situ GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano‐aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species. [ABSTRACT FROM AUTHOR]

Abstract: A combined experimental and theoretical investigation of Ag‐Pt sub‐nanometer clusters as heterogeneous catalysts in the CO→CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size‐selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first‐principles simulations at realistic coverage. In situ GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano‐aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metallic Co0 species in situ formed are suggested to be the main active sites for PDH. • CoO x but not Co0 is responsible for the formation of undesired products. • Transformation of CoO x to Co0 depends on the strength of CoO x -support interactions. • Co/Silicalite-1 showed the C 3 H 6 space time yield of 1.50 kg·h−1·kg cat −1 at 550 °C. Although Co-containing catalysts show attractive performance in the non-oxidative propane dehydrogenation to propylene (PDH), their tailored development is hindered by the ambiguity in the kind of active sites (Co0 or Co2+O x) responsible for selective and unselective pathways. Herein, we demonstrate that supported CoO x species expends its lattice oxygen through oxidation of C 3 H 8 to CO 2 /C 3 H 6 and are accordingly transformed into Co0 species. The latter are decisive for the selective dehydrogenation of propane to propylene with high activity. The ability of CoO x to in situ form Co0 is affected by metal-oxide-support interactions (MOSI). In addition to the kind of support, defective OH groups (OH nests) in ZSM-5-type zeolites seem to be relevant for the MOSI effect. In comparison with previous studies highlighting the importance of the size of CoO x species and their acidity for coke formation, we could not establish any direct correlation. Nevertheless, the presence of CoO x seems to be relevant for this undesired reaction because the formation of coke is hindered when CoO x species are transformed to Co0 species. Catalyst acidic sites are responsible for cracking reactions. Thus, the derived mechanistic insights reveal the nature of active sites both for selective and unselective pathways and provide fundamentals for catalyst development. From an industrial viewpoint, the developed Co/Silicalite-1 (Co/S-1) catalyst with the weakest MOSI and accordingly highest fraction of Co0 showed the space time yield of propylene formation of 1.50 kg·h−1·kg cat −1 at 67 % equilibrium propane conversion and propylene selectivity of 95.3 % and the Co-related TOF value of 0.145 s−1 at 550 °C. These both activity values exceed those of the state-of-the-art Co-containing catalysts. The productivity of Co/S-1 is comparable or even higher than that of industrially relevant Pt- or Cr-containing catalysts. [ABSTRACT FROM AUTHOR]

Gold-based catalysts have shown high catalytic activity for reverse water gas shift (RWGS) reactions at low temperatures. Despite extensive studies, the RWGS reaction on Au-based catalysts with very low Au content (< 0.1 wt%) has not yet been investigated. In this study, TiO 2 and ZrO 2 supported gold catalysts with such low gold loading have been synthesized and tested for RWGS. The catalysts were investigated by a series of in/ex-situ characterization techniques, including ICP-OES, XRD, BET, XPS, STEM, STEM-EELS, TAP, in-situ DRIFTS and in-situ EPR. At 250 oC, the Au/TiO 2 catalyst showed almost 10 times higher activity than Au/ZrO 2. In-situ DRIFTS results suggest that the formate mechanism is the predominant mechanism over Au/ZrO 2 , while over Au/TiO 2 the reaction proceeds via the formation of hydroxycarbonyl intermediates. A combined study including STEM, STEM-EELS, XPS, and in-situ EPR suggests that the interfacial Au–O v –Ti3+ sites are responsible for the superior activity of Au/TiO 2. [Display omitted] • Au/TiO 2 exhibited superior activity and CO selectivity. • Ti3+formation and oxygen vacancies on Au/TiO 2 contribute to its superior activity. • The weak adsorption strength of CO is responsible for the superior CO selectivity. • An Oxygen-vacancies-engaged reaction mechanism is proposed for RWGS over Au/ZrO 2. • The decomposition of formate seems to be the rate-limiting step in the CO formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gd, La and Sc improve stability of low Ni content Al 2 O 3 -MgO catalysts in DRM. • Rare earth elements stabilize Ni dispersion and promote CO 2 activation. • Gd sufficiently establishes both effects. • Outstanding stability in excess methane (CH 4 /CO 2 = 2) at 630 and 750 °C. • Successful exceptional long-term tests over 100 h at high space velocity. Biogas consists of a larger part of methane and a smaller part of carbon dioxide. Reforming biogas is highly desirable due to the direct conversion of the two components, yet not possible due to the current state of catalyst development. For such dry reforming of methane-rich gases (CH 4 /CO 2 = 2) we now present catalysts with low Ni loading (2.5 wt%) modified with Gd, Sc, or La. The best catalyst reaches 49% CH 4 conversion and 95% CO 2 conversion at 750 °C. The La-modification only shows limited influence on coking and protection against catalyst deactivation although this catalyst exposed highest basicity. On the other side, Sc- and especially Gd-modified catalysts exposed stronger metal-support interaction and thus enhanced stabilization of fine Ni particles during the reaction, which is critical to preserve high performance in CH 4 -rich DRM. This suppressed carbon deposition and the growth of structured carbon as evidenced by STEM images and TPO of spent catalysts. In this way, exceptionally high specific H 2 productivity (94 l/(g cat ·h)) compared to literature was obtained on Gd-modified catalyst, and, most noteworthy, after extending the time on stream from 8 to 100 h the amount of deposited coke increased only from 3 to 4 wt%. [ABSTRACT FROM AUTHOR]

We report on the manufacture of a state-of-the-art heterogeneous non-noble metal catalyst, which is based on a molecularly well-defined phosphine-tagged cobalt corrole complex. This precursor compound is readily synthesized from convenient starting materials while the active material is obtained through wet-impregnation of the pertinent metalliferous macrocycle onto carbon black followed by controlled pyrolysis of the loaded carrier material under an inert gas atmosphere. Thus, the obtained composite was then applied in the heterogeneous hydrogenation of various nitroarenes to yield a vast array of valuable aniline derivatives that were conveniently isolated as their hydrochloride salts. The introduced catalytic protocol is robust and user-friendly with the entire assembly of the reaction set-up enabling the conduction of the experiments on the laboratory bench without any protection from air. [ABSTRACT FROM AUTHOR]

• Rh supported large pore Zr-MOFs with different pore structure were prepared and characterized. • The catalysts show markedly different catalytic effects in the hydroformylation reaction with different framework types. • All catalysts show superior activity at low rh content as expected from rh single site catalysts. • A markedly impact of the pore structure on selectivity to aldehydes and enones is observed. • Catalytic differences are due to different accessibility of rh located in various framework sites. Three large pore crystalline zirconium-based metal-organic frameworks (Zr-MOFs) of different pore sizes (6–18 Å) and structure were synthesized and used for the preparation of the Rh-supported catalysts Rh@UiO-66, Rh@UiO-67, and Rh@MOF-808. The materials were characterized by XRD, FTIR, SEM/TEM, XPS, and nitrogen adsorption/desorption measurements. The catalytic performance was studied in the hydroformylation of olefins to the corresponding aldehydes. A series of n-alk-1-enes of different chain length was used to study the influence of the pore size and structure. The results show that the Zr-MOF-based catalysts are very active and show high aldehyde selectivity. The superior catalytic properties are assigned to the presence of highly dispersed active Rh sites located at the isolated zirconia moieties and the enhanced accessibility of sites via the large pores. Nevertheless, marked differences in the catalytic performance of the catalysts are observed, which are assigned to the different accessibility of Rh located at various secondary building units. [Display omitted] [ABSTRACT FROM AUTHOR]