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The direct auration of arenes is a key step in numerous gold‐catalyzed reactions. Although reported more than 100 years ago, understanding of its underlying mechanism has been hampered by the difficulties in the isolation of relevant intermediates given the propensity of gold(III) species to undergo reductive elimination. Here, we report the synthesis and isolation of a new family of intriguing zwitterionic [C(sp3)^C(sp2)]‐auracyclopentanes, as well as of their alkyl‐gold(III) precursors and demonstrate their value as mechanistic probes to study the C(sp2)‐Au bond‐forming event. Experimental investigations employing Kinetic Isotope Effects (KIE), Hammett plot, and Eyring analysis provided important insights into the formation of the auracycle. The data suggest a SEAr mechanism wherein the slowest step might be the π‐coordination between the arene and the gold(III) center, en route to the Wheland intermediate. We also show that these auracyclopentanes can work as catalysts in several gold‐promoted transformations. [ABSTRACT FROM AUTHOR]

Shape-controlled nanocrystals, such as nanoflowers, are expected to serve as innovative nanocatalysts with high catalytic activity. It is well-established that these nanocrystals can be readily synthesized with specific shapes using colloidal methods in solutions containing capping agents. However, these capping agents tend to reduce the catalytic activity of nanocatalysts. Therefore, it is imperative to remove these agents without altering the morphology to enhance catalytic efficiency. In this study, we developed a method for eliminating melamine, a common capping agent, from supported Au nanoflowers using water extraction and ultraviolet-ozone treatment. This process significantly enhances the catalytic performance, particularly for alcohol oxidation reactions such as the conversion of 1-phenylethyl alcohol to acetophenone. [ABSTRACT FROM AUTHOR]

This study presents a surface engineering strategy utilizing electronic waste (e‐waste) to incorporate single‐atom catalysts on conjugated polymers. Employing a conjugated porphyrin polymeric photocatalyst, gold single‐atom‐site catalysts are successfully introduced using the acidic metal leachates from e‐waste, where metal speciation and composition are regulated during the metal loading processes. The resulting photocatalyst with gold single atoms demonstrates a remarkable hydrogen peroxide (H2O2) selectivity of up to 97.56%, yielding a pure H2O2 solution at 73.3 µm h−1 under white LED illumination. The produced H2O2 is activated to •OH radicals on the same polymer with mixed gold and iron atoms, enabling a photo‐Fenton reaction and the complete degradation of toxic microcystin‐LR within 10 min under visible light. This study highlights the universal applicability of the metal mining strategy in various photoreactions. It is believed that this discovery pioneers sustainable photocatalysis, allowing the tuning of reactivity and selectivity on photocatalytic surfaces using metal waste. [ABSTRACT FROM AUTHOR]

[Display omitted] A herein proposed PdAu/Al 2 O 3 egg-shell catalyst for selective acetylene hydrogenation combines two factors to provide perfect performance: isolation of Pd 1 active sites by Au and an egg-shell distribution of the active phase across the catalyst pellets. The PdAu/Al 2 O 3 catalyst exhibits high acetylene hydrogenation activity at the level of Pd-catalysts and high intrinsic ethylene selectivity of Au-catalysts. [ABSTRACT FROM AUTHOR]

Utilizing sustainable electrocatalysis to upcycle glycerol (GLY; the by‐product of biodiesel) to lactic acid (LA; the key monomers for biodegradable polymer) is an efficient way to reduce the cost of biodiesel, which is also consistent with the waste‐to‐wealth principle. However, current research still suffers from issues of low LA selectivity (<80%), especially at high current density. Herein, we designed a cooperative catalyst by modifying BiOx nanolayers on gold nanoparticles (BiOx/Au), achieving high LA selectivity (82%) at high current density (226 mA cm−2 at 1.05 V vs. RHE), outperforming most of the reported works in the literature. We reveal that BiOx could promote the adsorption of the middle hydroxyl of GLY, which facilitates the formation of DHA and thus enables high LA selectivity. Moreover, the electron‐deficient Au in BiOx/Au is responsible for the enhanced current density, which is more beneficial to generate reactive oxygen species (OH*). To further reveal the application potential of this electrocatalytic strategy, we realized that the conversion of crude GLY extracted from cooking oil to LA coupled with H2 production using a membrane‐free flow electrolyzer, demonstrating a sustainable fashion to convert biodiesel waste into high value‐added product and H2 fuel. [ABSTRACT FROM AUTHOR]

Gold complexes, because of their unique carbophilic nature, have evolved as efficient catalysts for catalyzing various functionalization reactions of C–C multiple bonds. However, the realization of enantioselective transformations via gold catalysis remains challenging due to the geometrical constraints and coordination behaviors of gold complexes. In this context, merged gold/organocatalysis has emerged as one of the intriguing strategies to achieve enantioselective transformations which could not be possible by using a single catalytic system. Historically, in 2009, this field started with the merging of gold with axially chiral Brønsted acids and chiral amines to achieve enantioselective transformations. Since then, based on the unique reactivity profiles offered by each catalyst, several reports utilizing gold in conjunction with various chiral organocatalysts such as amines, Brønsted acids, N-heterocyclic carbenes, hydrogen-bonding and phosphine catalysts have been documented in the literature. This article demonstrates an up-to-date development in this field, especially focusing on the mechanistic interplay of gold catalysts with chiral organocatalysts. [ABSTRACT FROM AUTHOR]

As heterogeneous catalysts, nanoclusters have been extensively investigated because of their exceptional catalytic performance. In this work, we propose an electrostatic attraction strategy to immobilize atomically precise positively charged [Au52Cu72(SR)55]+ (denoted as Au52Cu72(SR)55) nanoclusters supported onto negatively charged SBA‐15. As expected, the Au52Cu72(SR)55/SBA‐15 catalysts display outstanding activity for driving the benzyl azide‐phenylacetylene cycloaddition reaction (called as click reaction). In comparison to Au11/SBA‐15 and Cu13/SBA‐15 catalysts, the bimetallic Au52Cu72(SR)55/SBA‐15 catalysts exhibit the highest catalytic activity for click reaction. Moreover, to explore the effect of ligands on the catalytic performance of Au52Cu72(SR)55/SBA‐15 catalysts, Au52Cu72(SR)55/SBA‐15‐X (X is the heat treatment temperature, X=120, 250, 300) catalysts are obtained by calcining at different temperatures. Compared with Au52Cu72(SR)55/SBA‐15‐X (X=120, 250, 300), the uncalcined Au52Cu72(SR)55/SBA‐15 catalysts show the best recyclability for click reaction. The structural integrity of the Au52Cu72(SR)55 nanoclusters is a key factor contributing to their exceptional cyclic performance. This work will be valuable for designing an ideal ligand‐protected clusters‐based catalysts with superior performance for organic reactions. [ABSTRACT FROM AUTHOR]

The use of gold nanoparticles (Au NPs) as catalysts has gained widespread attention in various reactions due to their high activity and selectivity under mild reaction conditions. However, one major challenge in utilizing these catalysts is their tendency to aggregate, leading to catalyst deactivation and hindering their amplification and industrial application. To overcome this issue, herein, we used a method by coating the surface of Au NPs with a thin layer of SiO2, which resulted in the formation of a superior catalyst denoted as Au@SiO2/ZA. Characterization studies revealed that the SiO2 layer is coated on the surface of Au NPs and effectively prevents the aggregation and growth of the gold particles during the reaction process, which makes the catalyst display excellent stability in furfural (FF) oxidative esterification to methyl furoate (MF). Moreover, the stabilization strategy is not limited to SiO2 alone. It can also be extended to other oxides such as ZrO2, CeO2, and TiO2. We believe this work will provide a good reference for the design and development of an efficient and stable gold catalyst for the oxidative esterification reaction. [ABSTRACT FROM AUTHOR]

The characterization and identification of the dynamics of cluster catalysis are crucial to unraveling the origin of catalytic activity. However, the dynamical catalytic effects during the reaction process remain unclear. Herein, we investigate the dynamic coupling effect of elementary reactions with the structural fluctuations of sub-nanometer Au clusters with different sizes using ab initio molecular dynamics and the free energy calculation method. It was found that the adsorption-induced solid-to-liquid phase transitions of the cluster catalysts give rise to abnormal entropy increase, facilitating the proceeding of reaction, and this phase transition catalysis exists in a range of clusters with different sizes. Moreover, clusters with different sizes show different transition temperatures, resulting in a non-trivial size effect. These results unveil the dynamic effect of catalysts and help understand cluster catalysis to design better catalysts rationally. [ABSTRACT FROM AUTHOR]

A Supported gold catalyst was prepared by reduction of HAuCl4 with the Cacumen Platycladi extract. This catalyst was then used for oxidation of 2-phenylethyl alcohol in a model reaction. Our study evaluated the effect of various preparation conditions, including the Au loading ratio and calcination temperature. Additionally, we explored the influence of the reaction temperature and reaction time on the catalytic performance of a Au/TiO2 catalyst. Our experimental findings revealed notable results for the Au/TiO2 catalyst characterized by the Au loading of 1.3 wt % and calcinated at 400°C. Under specific reaction conditions (0.3 g catalyst, 220°C, 3.0 MPa, 2.5 h), the conversion of 2-phenylethyl alcohol reached 45.3 and a 59.6% selectivity and a 27.0% yield of the target product (phenylacetaldehyde). In addition, catalytic performance remained stable after 8 repeated uses. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction reaction (CO2RR) gives an ideal approach for producing valuable chemicals, offering dual benefits in terms of environmental preservation and carbon recycling. In this work, a strong synergistic effect is constructed by adopting electron-rich graphdiyne (GDY) as the supporting matrix, which significantly stabilizes the Au active sites and boosts the CO2RR process. The as-prepared GDY-supported Au nanoparticles (Au/GDY) exhibit excellent CO2RR performance, with an extremely high faradaic efficiency of 94.6% for CO as well as good stability with continuous electrolysis for 36 hours. The superior activity and stability of the Au/GDY catalyst can be attributed to the electronic interaction between Au nanoparticles and the GDY substrate, resulting in enhanced electron transfer rates and a stable network of catalytically active sites that ultimately promote the CO2RR. [ABSTRACT FROM AUTHOR]

Synthesizing efficient and environment–friendly visible–light photocatalyst with simple methods is becoming attractive in these years in the field of photocatalysis. We report the preparation of Au@SbW9Co3 nanostructures, an environment-friendly visible–light catalyst, by coating Au0 with Polyoxometalate (POM) in a green and convenient way, the photocatalytic activities of which were investigated under visible light. The prepared Au@POM nanostructures showed the photocatalytic active in visible light region, which indicates a synergistic effect between POM and Au0. In addition, the morphology of Au@POM nanostructures, species of POM, the proportion of POM in catalyst and the concentration of Au@POM all affect the photocatalytic effect of catalysts. When the used POM was SbW9Co3, the molar ratio of Au3+:SbW9Co3 was 2:1.0 and the catalyst concentration was 0.15 mM, the highest photocatalytic effect was obtained, and the removal efficiency for EY reached 99% after catalyzing 60 min in visible light. [ABSTRACT FROM AUTHOR]

Water oxidation is one of the most important reactions needed for a transition to a green economy. The reaction relies on extracting electrons from oxygen anions and is commonly studied using homogenous catalysts based on Ru or Ir metals. Because of Ir scarcity and its relative instability in acidic environments, metals to replace it are sought after. In this study, we have synthesized Au-Pd-based catalysts deposited on TiO2 with different ratios in order to mimic IrO2 valence orbitals (Ir5d) by the hybrid valence orbitals of Au5d and Pd4d and compared their heterogeneous catalytic activity for the evolution of O2 from water in the presence of cerium ammonium nitrate (CAN). Au-Pd-based catalysts were found to be active at a particular nominal atomic ratio. At an atomic ratio of 1 Au to 2 Pd and 1 Au to 3 Pd, the catalysts were active and stable for oxygen production from water. Long-term runs up to 20,000 min still showed the expected stoichiometry between O2 production and CAN consumption (1 to 4). However, catalysts with a reverse ratio were not active. Also, the monometallic catalysts were found to be not active for the reaction. We link the reason for the activity of Au-Pd with this specific ratio to the shape and energy position of their valence band that might be similar to those of IrO2 particles. While the turnover numbers of the Au-Pd-based catalysts were found to be lower than those of IrO2-based catalysts, on the same support in a heterogenous system, there is considerable potential upon further optimization for these two metals to replace IrO2 for a water oxidation reaction. [ABSTRACT FROM AUTHOR]

Supported metal catalysts have attracted considerable attention because of their remarkably high catalytic activity and thermal stability. In this work, we report a facile and eco‐friendly method to synthesize porous Au/TiO2 nanocomposites with tunable size and different loading of Au nanoparticles. Porous TiO2 particles with average size of 20 nm were obtained using deep eutectic solvent‐assisted solvothermal method, in which Au NPs were immobilized by citrate reduction process. By adjusting the molar ratio of citrate and gold precursor, the size and loading of Au particles could be effectively controlled. The optimized nanocomposite with maximum Au loading and smallest particle size of 9 nm manifested the best catalytic activity in the 4‐nitrophenol reduction and excellent reusability. The superior catalytic performance can be ascribed to the strong interfacial interaction between small Au NPs and porous TiO2 support together with the high concentration of active sites at the interface. [ABSTRACT FROM AUTHOR]

Two different classes of stereoselective cyclizations have been developed using a chiral auxiliary approach with commercially available [JohnPhosAu(MeCN)SbF6] as catalyst. First, a stereoselective cascade cyclization of 1,5‐enynes was achieved using the Oppolzer camphorsultam as chiral auxiliary. In this case, a one‐pot cyclization‐hydrolysis sequence was developed to directly afford enantioenriched spirocyclic ketones. Then, the stereoselective alkoxycyclization of 1,6‐enynes was mediated by an Evans‐type oxazolidinone. A reduction‐hydrolysis sequence was selected to remove the auxiliary to give enantioenriched β‐tetralones. DFT studies confirmed that the steric clash between the chiral auxiliary and alkene accounts for the experimentally observed diastereoselective cyclization through the Si face. [ABSTRACT FROM AUTHOR]

The excellent catalytic performances of enzymes in terms of activity and selectivity are an inspiration for synthetic chemists and this has resulted in the development of synthetic containers for supramolecular catalysis. In such containers the local environment and pre‐organization of catalysts and substrates leads to control of the activity and selectivity of the catalyst. Herein we report a supramolecular strategy to encapsulate single catalysts in a urea‐functionalized Fe4L6 cage, which can co‐encapsulate a functionalized urea substrate through hydrogen bonding. Distinguished selectivity is obtained, imposed by the cage as site isolation only allows catalysis through π activation of the substrate and as a result the selectivity is independent of catalyst concentration. The encapsulated catalyst is more active than the free analogue, an effect that can be ascribed to transitionstate stabilization rather than substrate pre‐organization, as revealed by the MM kinetic data. The simple strategy reported here is expected to be of general use in many reactions, for which the catalyst can be functionalized with a sulfonate group required for encapsulation. [ABSTRACT FROM AUTHOR]

ChemCatChem homepage for more articles in the collection. The mechanism of the low‐temperature water gas shift reaction (LTWGS) on an Au/CeO2 catalyst was investigated by means of in situ diffuse reflectance infrared (DRIFT) spectroscopy. Under steady‐state LTWGS reaction (373–623 K), the catalyst is partially reduced, and signals from carbonate/formate dominates the infrared spectra. Time‐resolved pulse of CO experiment under a constant partial pressure of water at 423 K indicates that Ce4+ can be reduced to Ce3+ and that formate (HCOO) species cannot be directly related to the CO2 production. Further information was obtained by performing modulation excitation spectroscopy (MES) experiments coupled with a phase‐sensitive detection (PSD) method. Under periodic modulation of the CO partial pressure while keeping the H2O concentration constant, most of the intense bands of carbonate and formate remained constant, indicating that these species are only spectators. The same is observed for the concentration of Ce3+. Conversely, signals in‐phase with the conversion of CO to CO2 are observed and assigned to carboxyl [C(O)OH] and carboxylate (CO2δ−) species, while some monodentate formate (m‐HCOO) also changes but at a lower rate. A plausible associative reaction mechanism where carboxyl/carboxylate are key intermediates is postulated. [ABSTRACT FROM AUTHOR]

Precious metal (PM) catalysts have been widely used in the chemical industry owing to their high activity, selectivity and stability. The key problems are their scarcity and high cost. Therefore, the recycling of PMs from deactivated catalysts becomes a critical step in industry. Here, we developed a novel recycling method for the photoresponsive carrier-supported Au-based PM catalyst through an eco-friendly photocatalytic dissolution technique. Au is recovered effectively from deactivated Au/CeO2 using itself as the photocatalyst and re-deposited on the remaining CeO2. The revived Au/CeO2 exhibits comparable performance with the fresh catalyst during ethane dehydrogenation either in the absence or in the presence of CO2. Similar results can also be obtained over the Pt/CeO2 catalyst recovered from a deactivated catalyst using this all-in-one dissolution-deposition technique. In comparison with the conventional methods, this recycling preparation offers a more environmentally friendly and long-lasting method for efficiently recycling PMs and producing regenerated PM catalysts. [ABSTRACT FROM AUTHOR]

Camposeco et al. [[14]] developed highly efficient Au/ZnO-ZrO SB 2 sb catalysts for CO oxidation at a low temperature. The catalysts were evaluated for total propane oxidation, with the Fe SB 0.50 sb Mn SB 0.50 sb O SB x sb catalyst being the most active for propane oxidation. 10.3390/catal13050834 6 Shah P.M., Bailey L.A., Morgan D.J., Taylor S.H. The Effect of Metal Ratio and Precipitation Agent on Highly Active Iron-Manganese Mixed Metal Oxide Catalysts for Propane Total Oxidation. It is shown that the catalysts obtained with treated ZSM-5 exhibit higher activity in the reactions of propane, and that n-hexane completes oxidation as opposed to the catalyst samples containing un-treated zeolite. [Extracted from the article]

The low-temperature water-gas-shift (LT-WGS) reaction has shown remarkable activity for Au single-atom supported on reducible oxide catalysts. The water dissociation step of the WGS reaction is calculated using density functional theory (DFT) over four single Au atom (Au 1)-pristine reversible oxides support systems Au 1 /M a O b -O v (Au 1 /TiO 2- x , Au 1 /ZrO 2- x , Au 1 /CeO 2- x and Au 1 /Co 3 O 4- x) system and four Au 1 -supports with O vacancy (O v) systems Au 1 /M a O b (Au 1 /TiO 2 , Au 1 /ZrO 2 , Au 1 /CeO 2 and Au 1 /Co 3 O 4). According to its greatest H 2 O adsorption energy, lowest water dissociation barrier, and slightest structural distortion, Au 1 /CeO 2- x is chosen as the most beneficial catalyst for the WGS process. Afterwards, for Au 1 /CeO 2- x , three reaction pathways (redox path, formate path and carboxyl path) are calculated. The predominant reaction pathway is the carboxyl pathway, and hydrogen production is the rate-determining step (RDS). For the purpose of designing single metal-support catalysts for the LT-WGS reaction, this paper gives information on the strong metal-support interaction (SMSI). [Display omitted] • LT-WGS reaction on Au 1 single atom supported on four metal oxides is carried out. • The oxygen vacancy (O v) of oxide support plays a key role in Au 1 stabilization. • H 2 O dissociates on O v and Au 1 /CeO 2- x has the lowest H 2 O dissociation energy. • Au 1 /CeO 2- x takes carboxyl path, H 2 generation is the rate limiting step. [ABSTRACT FROM AUTHOR]

The preferential oxidation of CO in H 2 is attractive for the removal of trace amounts of CO to meet the requirement of proton-exchange membrane fuel cells (PEMFCs) application. The key is to design highly effective catalysts that work well in a wide range of low temperatures. Here, the recent progress in Au and Pt group metal catalysts for the PROX reaction is summarized, covering those with single-atom and cluster dispersed metal species with remarkable performance. Firstly, the progress of some representative catalysts is overviewed, with an emphasis on the strategies for improving low-temperature activity, selectivity, and stability. Then, special attention is focused on the key parameters affecting performance in the PROX reaction. Moreover, the reaction mechanisms in terms of adsorption and activation of reactants are discussed. Finally, the challenges and opportunities are offered for guiding the design of advanced noble metal catalysts toward the PROX process. [Display omitted] • Single-atom and cluster catalysts for preferential oxidation of CO in H 2 are reviewed. • Strategies were proposed for improving low-temperature activity, selectivity, and stability. • Key factors of particle size, metal-support interaction, and the role of hydroxyl species were discussed. • Reaction mechanisms based on adsorption and activation of reactants are depicted. [ABSTRACT FROM AUTHOR]

An azobenzene-bearing N-heterocyclic carbene-based gold catalyst is reported of which the reactivity in a cyclization reaction depends on the isomeric state of the azobenzene. The configurations of the catalyst can be reversibly switched by light and are stable during the reaction, effectively leading to a switchable catalyst system. [ABSTRACT FROM AUTHOR]

[Display omitted] Covalent organic frameworks (COFs) are excellent candidates for rationally designed metal-coordinated catalysts due to their porous structures and adjustable organic building blocks. In this work, a two-dimensional (2D) COF with novel fxt topology was synthesized. The newly devised COF had been fully characterized by a range of spectroscopic and microscopic techniques. The COF was further metallized by the gold species to form a heterogeneous catalyst that enabled the one-pot synthesis of flavone and its derivatives. The Au@COF catalyst showed high catalytic activity and good recyclability. This work demonstrates the great potential of metallized COFs with unique well-defined pores in organic catalysis. [ABSTRACT FROM AUTHOR]

Multimetallic catalysis is a powerful strategy to access complex molecular scaffolds efficiently from easily available starting materials. Numerous reports in the literature have demonstrated the effectiveness of this approach, particularly for capitalizing on enantioselective transformations. Interestingly, gold joined the race of transition metals very late making its use in multimetallic catalysis unthinkable. Recent literature revealed that there is an urgent need to develop gold-based multicatalytic systems based on the combination of gold with other metals for enabling enantioselective transformations that are not possible to capitalize with the use of a single catalyst alone. This review article highlights the progress made in the field of enantioselective gold-based bimetallic catalysis highlighting the power of multicatalysis for accessing new reactivities and selectivities which are beyond the reach of individual catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Depth-controlled TiO 2 nanotraps are constructed by an area-selective atomic layer method. • TiO 2 nanotrap's depth determines both the exposed sites and the electronic states of Au. • The particle migration-coalescence of Au can be suppressed by TiO 2 nanotraps. • Balance between stability and activity of Au can be achieved by tuning nanotraps' depth. The sintering of nanoparticles has always been a great challenge for supported Au catalysts. Herein, we fabricate a depth-controlled TiO 2 nanotrap via area-selective atomic layer deposition (ALD) method to balance the activity and anti-sintering properties of Au nanoparticles. Au nanoparticles anchored by a 2.31 nm deep TiO 2 nanotrap prepared by 25 ALD cycles of TiO 2 exhibit the best overall activity for CO oxidation, where the depth of TiO 2 nanotrap is close to the geometric radius of Au nanoparticle. It exhibits enhanced sintering resistance while retaining an activity similar to that of pure Au catalyst. The average size of sintered Au (8.4 ± 2.7 nm) is three times smaller than that of pure Au catalyst (21.1 ± 7.1 nm) after calcination in air at 700 °C. The performance of TiO 2 nanotrapped Au catalyst breaks the conventional trade-off between the activity and anti-sintering capability of Au by exposing active sites, and hindering Au migration-coalescence simultaneously, which serves as a promising strategy to design highly stable Au catalysts. [ABSTRACT FROM AUTHOR]

High activity of a catalyst and its thermal stability over a lifetime are essential for catalytic applications, including catalytic gas sensors. Highly porous materials are attractive to support metal catalysts because they can carry a large quantity of well-dispersed metal nanoparticles, which are well-accessible for reactants. The present work investigates the long-term stability of mesoporous Co3O4-supported Au–Pd catalyst (Au–Pd@meso-Co3O4), with a metal loading of 7.5 wt% and catalytically active mesoporous Co3O4 (meso-Co3O4) for use in catalytic gas sensors. Both catalysts were characterized concerning their sensor response towards different concentrations of methane and propane (0.05–1%) at operating temperatures ranging from 200 °C to 400 °C for a duration of 400 h. The initially high sensor response of Au–Pd@meso-Co3O4 to methane and propane decreased significantly after a long-term operation, while the sensor response of meso-Co3O4 without metallic catalyst was less affected. Electron microscopy studies revealed that the hollow mesoporous structure of the Co3O4 support is lost in the presence of Au–Pd particles. Additionally, Ostwald ripening of Au–Pd nanoparticles was observed. The morphology of pure meso-Co3O4 was less altered. The low thermodynamical stability of mesoporous structure and low phase transformation temperature of Co3O4, as well as high metal loading, are parameters influencing the accelerated sintering and deactivation of Au–Pd@meso-Co3O4 catalyst. Despite its high catalytic activity, Au–Pd@meso-Co3O4 is not long-term stable at increased operating temperatures and is thus not well-suited for gas sensors. [ABSTRACT FROM AUTHOR]

Direct galvanic replacement of surface Cu with Au3+ in PtCu3 nanodendrites is applied to synthesize an Au-modified PtCu3 nanodendrite catalyst (PtCu3–Au), which shows both superior stability and excellent activity for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). The PtCu3–Au catalyst only lost 7% of its MOR activity and its ORR half-wave potential decreased 8 mV after 10 000 potential cycles. [ABSTRACT FROM AUTHOR]

Gold‐catalyzed cyclizations of (2‐formylphenyl)prop‐2‐yn‐1‐yl acetates afford two distinct cyclization products. In the case of substrates bearing a alkyl or arylalkynyl group, 2‐carbonyl‐1H‐indene derivatives were obtained whereas substrates bearing an electron‐withdrawing alkynoate or alkynone group, distinct 4‐acetoxy‐3‐hydroxy‐2‐naphthoates were produced efficiently. Our mechanistic analysis indicates that H2O is not only a nucleophile but also a catalyst for both carbocyclizations. [ABSTRACT FROM AUTHOR]

The catalytic conversion of greenhouse gases, such as N2O, is a promising way to mitigate global warming. In this work, density functional theory (DFT) studies were performed to study N2O reduction by CO over single-atom catalysts (SACs) and compare the performance of noble (Au/C2N) and non-noble (Cu/C2N) SACs. The computational results indicated that catalytic N2O reduction on both catalysts occurs via two mechanisms: (I) the N2O adsorption mechanism—starting from the adsorption on the catalysts, N2O decomposes to a N2 molecule and O-M/C2N intermediate, and then CO reacts with O atom on the O-M/C2N intermediate to form CO2; and (II) the CO adsorption mechanism—CO and N2O are adsorbed on the catalyst successively, and then a synergistic reaction occurs to produce N2 and CO2 directly. The computational results show that mechanism I exhibits an obvious superiority over mechanism II for both catalysts due to the lower activation enthalpy. The activation enthalpies of the rate-determining step in mechanism I are 1.10 and 1.26 eV on Au/C2N and Cu/C2N, respectively. These results imply that Cu/C2N, an abundant-earth SAC, can be as active as expensive Au/C2N. Herein, our research provides a theoretical foundation for the catalytic reduction of N2O and broadens the application of non-noble-metal SACs. [ABSTRACT FROM AUTHOR]

Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS2/Au heterojunctions were successfully synthesized by reduction of chloroauric acid in the solution of layered MoS2 prepared by hydrothermal method. As a model molecule, methylene blue (MB) was used as the species to be degraded to evaluate the performance of the catalyst. It was determined by UV–visible spectra that the optimal catalyst can be obtained when MoS2 (mg): HAuCl4 (wt. % mL) is 2:2. The Fenton-like reaction process was monitored by introducing highly sensitive surface enhanced Raman spectroscopy (SERS). The results show that MB can be degraded by 83% in the first 10 min of the reaction, indicating that MoS2/Au has good catalytic performance. In addition, as a fingerprint spectrum, SERS was used to preliminarily analyze the molecular structure changes during the degradation process. The result showed that C-N-C bond was easier to break than the C-S-C bond. NH2 group and the fused ring were destroyed at the comparable speed at the first 30 min. In terms of application applicability, it was showed that MB degradation had exceeded 95% at all the three pH values of 1.4, 5.0, and 11.1 after the reaction was carried out for 20 min. The test and analysis of the light environment showed that the catalytic efficiency was significantly improved in the natural light of the laboratory compared to dark conditions. The possible mechanism based on ·OH and ·O2− from ESR data was proposed. In addition, it was demonstrated to be a first-order reaction from the perspective of kinetics. This study made a positive contribution to broaden of the applicable conditions and scope of Fenton-like reaction catalysts. It is expected to be used as a non-iron catalyst in practical industrial applications. From the perspective of detection method, we expect to develop SERS as a powerful tool for the in situ monitoring of Fenton-like reactions, and to further deepen our understanding of the mechanism. [ABSTRACT FROM AUTHOR]

The nanorod shaped (Pt−Au)/CeO2 catalysts with varied Pt/Au ratio were achieved from Al91.7Ce8AuXPt0.15−X (X=0.05, 0.075, 0.1) precursor alloys through combined dealloying and calcination treatment. The surface morphology, microstructure as well as physicochemical features were characterized through XRD, SEM, TEM, XPS, Raman spectroscopy and N2 adsorption‐desorption tests. The catalytic measurement results imply that the (Pt0.075−Au0.075)/CeO2 catalyst displays optimal catalytic property with 50% and 99% reaction temperature as low as 37 °C, 80 °C, respectively. The (Pt0.075−Au0.075)/CeO2 was also stable after 60 h successive catalytic oxidation reaction. The outstanding catalytic performance is ascribed to the joint introduction of Pt and Au, which can suppress the agglomeration and growth of noble metal active phases during the catalytic process. What's more, the nanoscale interface formed between Pt&Au nanoparticles and CeO2 nanorods can also promote electron transfer rate, thus catalytic reaction efficiency is enhanced. The results will be of importance for design of novel nanoporous noble metal‐oxide‐based catalysts and application in exhaust treatment of fuel vehicles. [ABSTRACT FROM AUTHOR]

A simple and efficient photocatalytic approach for dehydrative etherification of alcohols has been developed by a nanoporous gold catalyst. This protocol features no requirement of addition of acids or bases, broad substrate generality, and excellent acid-sensitive functional group tolerance. The mechanistic studies demonstrate the heterogeneous nature of the catalytic system and the recyclability of the catalyst was demonstrated repeatedly. [ABSTRACT FROM AUTHOR]

Background: The sustainable conversion of biomass‐derived glycerin into high‐value‐added chemicals is a significant challenge in contemporary science. In this context, the selective oxidation of aqueous glycerin into glyceric acid was investigated in the presence of NaOH and atmospheric oxygen. It was demonstrated that the selective transformation of glycerin to glyceric acid involves a new chemical reaction path for commodity glyceric acid that is both abundant and economical. Results: The hydrotalcite‐supported Au nanoparticle catalyst (5%Au/HT) was found to be the most active for glycerin selective transformation to glyceric acid, showing 89.5% glycerin conversion with 61.2% glyceric acid selectivity under optimum experimental conditions. Furthermore, the 5%Au/HT catalyst was reused six times and maintained nearly the same activity in the catalytic recycle experiments. Conclusion: In the Au‐based catalysts, there are strong electronic interactions between the different supports and Au nanoparticles (Au NPs). Besides, the basic sites of the catalysts participated in promotion of hydroxyl functional groups. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Expensive gold‐based catalysts are frequently used for electrochemical CO2 reduction into CO. A feasible approach to obtain low‐cost Au‐based catalysts is needed. Herein, a novel framework 1 assembled from [Zr48Ni6] nano‐cages is prepared. It exhibits a high BET surface area of 1569 m2 g−1 and high solvents/pH stability. 1 can not only selectively extract AuCl4− from artificial electronic waste, but can then be transformed into low‐cost catalyst Au nanoparticle@1‐x (Au NPs@1‐x, x=1, 2, 3, 4) with tuneable Au NPs sizes. The CO2RR investigations revealed that the Au NPs@1‐3 displayed an excellent FECO of 95.2 % with a current density of 102.9 mA cm−2 at −1.1 V, and such high catalytic activity can be maintained for at least 15 h without obvious decrease because the confinement effect of [Zr48Ni6] nano‐cages prevents Au NPs agglomeration. This work offers a facile strategy to obtain low‐cost and high‐performance Au‐based catalysts for various reactions activated by Au. [ABSTRACT FROM AUTHOR]

A series of γ-Al 2 O 3 supported gold-palladium (Au-Pd) alloy nanoparticles (NPs) catalysts were synthesized by a one-pot approach applying mercapto-propyl-trimethoxysilane (MPTMS) as an anchoring ligand. Homogeneously dispersed Au-Pd alloy NPs were observed on the prepared catalysts and their catalytic performance in benzyl alcohol partial oxidation was investigated. Results showed that the highest benzaldehyde yield was achieved on catalyst Au-Pd/7%MPTMS-γ-Al 2 O 3 with a benzaldehyde selectivity of 90%. By establishing the structure-performance relationship, the high activity of catalysts with MPTMS modification was attributed to the anchoring and dispersion effect of MPTMS on Au-Pd NPs, while the high benzaldehyde selectivity was due to the formation of more surface Lewis acid sites after introducing MPTMS, protecting the benzaldehyde from over-oxidation to byproducts. [Display omitted] • The presence of MPTMS led to well-dispersed Au-Pd alloy nanoparticles on alumina support. • The introduction of MPTMS produced more surface Lewis acid sites. • Lewis acid sites interacted with benzaldehyde, inhibiting over-oxidation and achieving high benzaldehyde selectivity. [ABSTRACT FROM AUTHOR]

The nature and local environment of Au single atoms supported and stabilized on four different oxides is studied by means of DFT + U calculations using CO as probe molecule and its stretching frequency, ωe, as a fingerprint of the site where the Au atom is bound. Four oxides are considered, anatase TiO2, tetragonal ZrO2, cubic CeO2, and a perovskite LaFeO3. In this latter case a recently reported experimental study has detected a stretching mode for CO adsorbed on Au1/LaFeO3 of 2215 cm−1, with a large blue shift, ∆ω(CO) = 72 cm−1 with respect to free CO. In order to identify the Au adsorption site that can give rise to this large blue-shift we have considered five cases: (a) Au replacing a lattice cation, (Au)subM; (b) Au replacing a lattice O anion, (Au)subO; (c) Au adsorbed on the surface, (Au)ads; (d) Au bound to an extra O atom on the surface, (AuO)ads, or (e) Au bound to two extra O atoms on the surface, (AuO2)ads. It turns out that the correct reproduction of ∆ω for CO adsorbed on positively charged gold, Auδ+, is challenging for DFT. Therefore, we have performed a comparative study of Auδ+-CO molecular compounds for which ωe(CO) is known experimentally using various kinds of DFT functionals and accurate CCSD and CCSD(T) quantum chemistry methods. Also based on this comparison we propose a tentative assignment for the observed frequency of CO adsorbed on Au1/LaFeO3 single atom catalyst. [ABSTRACT FROM AUTHOR]

The noble metal nanoparticles have attracted attention due to their excellent catalytic performance for CO oxidation at low temperatures. M-CeO2 (M = Pd, Ag, Au) catalysts with different atomic ratios of M/Ce were deposited via solution combustion method. Among them, 3 at% Pd-CeO2, 5 at% Ag-CeO2 and 1 at% Au-CeO2 catalysts have better catalytic performances. Especially, 5 at% Ag-CeO2 catalyst shows better low-temperature CO oxidation performance. The catalytic activity for CO oxidation follows the follows the following sequence: 5 at% Ag-CeO2 (T50 = 69 °C) > 3 at% Pd-CeO2 (T50 = 99 °C) >1 at% Au-CeO2 (T50 = 115 °C). Meanwhile, the catalysts are characterized by means of powder x-ray diffraction, scanning electron microscope, transmission electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Brunauerâ€"Emmettâ€"Teller and H2-TPR. The characterization results show that the 5 at% Ag-CeO2 catalyst has excellent catalytic activity due to the good dispersion of Ag nanoparticles, the specific surface area of the material, and the reduction catalyst between different valence ions. Moreover, the surface of the catalyst enhances the mutual synergy, effectively promotes the generation of oxygen vacancies, and increases the active oxygen content of the catalyst surface. Finally, the catalytic mechanism of M-CeO2 catalysts is summarized. [ABSTRACT FROM AUTHOR]

Heterogeneous catalysts based on metallic nanoparticles are promising candidates for wastewater treatment. However, they aggregate easily as a result of their high surface energy. Polymers are very popular supporting catalyst materials because they can stabilize the metallic nanoparticles to prevent aggregation. In this study, aniline-pentamer-based electroactive polyurea (EPU) was synthesized by oxidative coupling, and Au nanoparticles were anchored to the EPU via its aniline segments. Electrochemical redox behavior of the as-synthesized EPU was monitored by electrochemical cyclic voltammetry. The Au/EPU composite was characterized by FTIR, UV–vis, TGA, SEM, TEM, XRD XPS, and ICP-OES. SEM showed that the EPU had a flower-like structure, and the Au nanoparticles were uniformly immobilized on the EPU surface. The reduction of 4-nitrophenol (4-NP) by NaBH4 was used as a model reaction to evaluate the catalytic properties of the Au/EPU composite. Moreover, the optimization of the reaction conditions for the reduction of 4-NP to 4-aminophenol (4-AP) were also studied in detail. The Au/EPU composite catalyzed the reduction of 4-NP to 4-AP within 4 min with a rate constant of 2.4 × 10–2 s−1 and an activation energy of 40.17 kJ/mol. The Au/EPU composite demonstrated high conversion (98%) after 20 successive cycles. [ABSTRACT FROM AUTHOR]

We propose a simple way to synthesize gold catalysts consisting of dominant ca. 2 nm nanoparticles and single atoms on different carbons by the use of L‐arginine‐Au(III) complexes. The decomposition of the precursor proceeds via concurrent anchoring surface amine groups and forming gold species. The gold catalyst supported on a commercial nitrogen free carbon of the Sibunit family showed excellent activity in the gas phase formic acid decomposition reaction and 100 % selectivity towards hydrogen formation as compared to gold catalysts supported on nitrogen free and nitrogen doped carbon nanofibers and nanotubes. The observed increase in the reaction rate by a factor of up to 15 is due to the enrichment of external Sibunit surface with gold and surface amine groups. The intrinsic nitrogen centers of the nitrogen doped carbons are not sensitive to the gold precursor, thus not affecting the dispersion of gold and even deteriorating the catalyst activity. [ABSTRACT FROM AUTHOR]

Bioorthogonal chemistry introduces nonbiogenic reactions that can be performed in biological systems, allowing for the localized release of therapeutic agents. Bioorthogonal catalysts can amplify uncaging reactions for the in situ generation of therapeutics. Embedding these catalysts into a polymeric nanoscaffold can protect and modulate the catalytic activity, improving the performance of the resulting bioorthogonal "polyzymes". Catalysts based on nontoxic metals such as gold(I) are particularly attractive for therapeutic applications. Herein, we optimized the structural components of a metal catalyst to develop an efficient gold(I)-based polyzyme. Tailoring the ligand structure of gold phosphine-based complexes, we improved the affinity between the metal complex and polymer scaffold, resulting in enhanced encapsulation efficiency and catalytic rate of the polyzyme. Our findings show the dependence of the overall polyzyme properties on the structural properties of the encapsulated metal complex. [ABSTRACT FROM AUTHOR]

Two catalytic annulations of non-symmetric diarylketenes with thioalkynes are described using gold and phosphine catalysts respectively. We employed α-aryldiazo ketones to generate gold-π-ketenes, ultimately yielding azulen-1-one derivatives. With the same reactants, we utilized P(C6F5)3 to increase the yields of 1-naphthols, notably with a complete regioselectivity. [ABSTRACT FROM AUTHOR]

This work describes the empirical screening of base types and amounts on the catalytic property of gold‐polymer composite particles in the aerobic homocoupling of arylboronic acid. As these particles notably improve the yields of biaryl in the presence of bases, various bases and their amounts are systematically tested to experimentally identify an ideal base that can provide high reactivity and recyclability of the composite particles in mild and green conditions. Interestingly, the following conditions ‐ soluble strong bases at sub‐stoichiometric quantities (0.5 eq.) and insoluble weak bases at excess amounts (3.0 eq.) in EtOH ‐ significantly enhance the catalytic activities of the composite particles. Upon screening two ideal bases, overall catalytic properties of the composite particles including reaction rate at three different temperatures, activation energy (51–52 kJ/mole), and recyclability (7 cycles) were compared. Understanding the effect of bases and fine‐tuning reaction conditions can potentially improve overall reactivity and recyclability of the composite particles as a green quasi‐homogenous catalyst. [ABSTRACT FROM AUTHOR]

In this work, a new heterogeneous catalyst, comprising gold supported on DABCO-triazole ionic liquid-modified magnetic nanoparticles (Fe3O4@DT-Au), is developed for A3-coupling reaction. This nano-catalyst is characterized using different techniques, such as TEM, SEM, SEM-elemental mapping, XRD, XPS, and TGA. Using a 0.05 mol% of this catalyst, the three-component reaction of amines, aldehydes and alkynes is efficiently performed at 40 °C in water. This catalyst is easily recovered and recycled through external magnetic forces for six times with a small decrease in the activity and re-used catalyst was characterized. [ABSTRACT FROM AUTHOR]

In this study, 3D-structured NiMo coatings have been constructed via the widely used electrodeposition method on a Ti surface and decorated with very small Au crystallites by galvanic displacement (Au(NiMo)/Ti). The catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma optical emission spectroscopy. Different Au(NiMo)/Ti catalysts, which had Au loadings of 1.8, 2.3, and 3.9 µgAu cm−2, were prepared. The electrocatalytic activity of the Au(NiMo)/Ti catalysts was examined with respect to the oxidation of glucose in alkaline media by cyclic voltammetry. It was found that the Au(NiMo)/Ti catalysts with Au loadings in the range of 1.8 up to 3.9 µgAu cm−2 had a higher activity compared to that of NiMo/Ti. A direct glucose-hydrogen peroxide (C6H12O6-H2O2) single fuel cell was constructed with the different Au-loading-containing Au(NiMo)/Ti catalysts as the anode and Pt as the cathode. The fuel cells exhibited an open circuit voltage of ca. 1.0 V and peak power densities up to 8.75 mW cm−2 at 25 °C. The highest specific peak power densities of 2.24 mW µgAu−1 at 25 °C were attained using the Au(NiMo)/Ti catalyst with the Au loading of 3.9 µg cm−2 as the anode. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is recognized as one of the most emitted indoor air pollutants with high detrimental effect on human health. Significant research efforts are focused on HCHO removal to meet emission regulations in an effective and economically profitable way. For over three decades, the unique electronic properties and catalytic abilities of nano-gold catalysts continue to be an attractive research area for the catalytic community. Recently, we reported that mechanochemical mixing is a relevant approach to the preparation of Co-Ce mixed oxides with high activity in complete benzene oxidation. A trend of higher surface defectiveness, in particular, oxygen vacancies, caused by close interaction between cobalt oxide and cerium oxide phases, was observed for a mixed oxide composition of 70 wt.% Co3O4 and 30 wt.% CeO2. These results directed further improvement by promotion with gold and optimization of mixed oxide composition, aiming for the development of an efficient catalyst for room temperature HCHO abatement. Support modification with potassium was studied; however, the K addition caused less enhancement of HCHO oxidation activity than expected. This motivated the preparation of new carrier material. In addition to Co3O4-CeO2 mixed metal oxides with preset ratio, γ-Al2O3 intentionally containing 33% boehmite and shortly named Al2O3-b was used for synthesis. Analysis of the role of support composition in HCHO oxidation was based on the characterization of nano-gold catalysts by textural measurements, XRD, HRTEM, XPS, and TPR techniques. Gold supported on mechanochemically treated Co3O4-CeO2-Al2O3-b (50 wt.% Al2O3-b) exhibited superior activity owing to high Ce3+ and Co3+ surface amounts and the most abundant oxygen containing species with enhanced mobility. This catalyst achieved oxidation to CO2 and H2O by 95% HCHO conversion at room temperature and 100% at 40 °C, thus implying the potential of this composition in developing efficient catalytic materials for indoor air purification. [ABSTRACT FROM AUTHOR]

Catalysts based on gold nanoclusters supported by different materials have been used for the selective semihydrogenation of phenylacetylene to styrene. The most active species were formed by catalyst thermal activation in a reductive atmosphere. It is shown that the activity and selectivity of these catalysts is mainly controlled by the interaction of the gold nanoclusters with the support, as demonstrated by using materials with high surface area and different acidity/basicity, i.e. MgO, Al 2 O 3 and Mg/Al hydrotalcite. There is an important influence of the acid/base properties of the support on the selectivity. Higher activity is obtained for gold supported on basic materials (MgO and hydrotalcite) and the best results are obtained with the Au catalyst supported on the MgAl hydrotalcite exhibiting high activity and the best selectivity to the alkene. This was explained by the intermediate basicity of the support that favors the heterolytic cleavage of H 2 while avoiding the overreduction of the alkynes to alkanes. [Display omitted] [ABSTRACT FROM AUTHOR]

The existence of various surface active sites within a nanocrystal (NC) catalyst complicates understanding their respective catalytic properties and designing an optimal catalyst structure for a desired catalytic reaction. Here, we developed a novel approach that allows unequivocal investigation on the intrinsic catalytic reactivity of the edge and terrace atoms of NCs. Through the comparison of the catalytic behaviors of edge‐covered Pd NCs, which were prepared by the selective deposition of catalytically inactive Au atoms onto the edge sites of rhombic dodecahedral (RD) Pd NCs, with those of the pristine RD Pd NCs toward alkyne hydrogenation and Suzuki–Miyaura coupling reactions, we could decouple the activity of the edge and {110}‐plane atoms of the Pd NCs without uncertainties. We expect that this study will provide an opportunity to scrutinize the surface properties of various NC catalysts to a more precise level and devise ideal catalysts for intended catalytic reactions. [ABSTRACT FROM AUTHOR]