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We designed and constructed a beamline BL36XU at the 8 GeV synchrotron radiation facility SPring‐8 to provide information required for the development of next‐generation polymer electrolyte fuel cells (PEFCs) by clarifying the dynamic aspects of structures and electronic states of cathode catalysts under PEFC operating conditions and in the deterioration processes by accelerated durability test protcols. To investigate the mechanism and degradation process for the cathode electrocatalysis in practical PEFCs, we developed advanced time‐ and spatially‐resolved in‐situ/operando X‐ray absorption fine structure measurement systems and complementary analytical systems (X‐ray emission spectroscopy (XES), X‐ray diffraction (XRD), X‐ray computer tomography (CT) and hard X‐ray photoelectron spectroscopy (HAXPES)) and combined them to develop multi‐analytical systems at BL36XU. Multi‐analytical systems are very powerful for observing spatial‐temporal features of the transient processes occurring in complex systems such as PEFCs. This account describes the design, performance, and research results of the BL36XU and multi‐analytical in‐situ/operando systems. [ABSTRACT FROM AUTHOR]

Abstract: Operando time-resolved X-ray absorption fine structure (XAFS) analysis is promising to investigate the structural kinetics of cathode events on polymer electrolyte fuel cell (PEFC) electrocatalysts. Here we reviewed our recent reports on operando time-resolved XAFS analysis for PEFC cathode catalysts under PEFC operating conditions. Systematic analysis of a series of operando time-resolved XAFS (XANES and EXAFS) spectra showed details of the structural transformations of Pt cathode catalysts (Pt/C, Pt3Co/C, and Pt3Ni/C) in PEFC, and the rate constants of various structural parameters of the Pt cathode catalysts such as electron transfer from/to Pt (oxidative/reductive electron density change of Pt), Pt-O bond formation/breaking, and Pt-Pt bond breaking/reformation of the cathode catalysts were successfully obtained to discuss the mechanisms of the redox processes of the Pt cathode catalysts and the degradation behaviors of the Pt cathode catalysts in PEFC cells. In this paper, we discuss about structural kinetics of the Pt cathode catalysts in PEFC suggested by operando time-resolved XAFS analysis in the viewpoints of the effects of Pt alloying and degradation.Graphical Abstract: [ABSTRACT FROM AUTHOR]

DFT calculations were used to investigate the structure of the active Pt cluster and the catalytic reaction pathway for the selective synthesis of phenol from benzene and molecular oxygen regulated with ammonia on a Pt cluster/β-zeolite catalyst that was reported to be active for the selective hydroxylation of benzene only in the coexistence of ammonia. It was found that Pt5-Pt6 clusters were active for the direct synthesis of phenol, and they provided the reaction sites for bond rearrangements among ammonia, oxygen, and benzene; furthermore, the coexistence of ammonia was crucial for the selective oxidation of benzene to phenol, as it suppressed benzene combustion to CO2 and promoted the selective synthesis of phenol. It was further found that water coexisting in the system also played a significant role in desorbing phenol on the Pt cluster surface, which resulted in promotion of the overall selective synthesis of phenol. The energy diagram for the reaction sequences and the structures of the transition states were obtained, which indicated the origin of the Pt/β catalysis. [ABSTRACT FROM AUTHOR]

The account article treats with the characterizations of the structural and electronic transformations of Pt/C, PtCo/C, and PtNi/C cathode electrocatalysts in polymer electrolyte fuel cells (PEFCs) involving Pt charging/discharging, Pt-O bond formation/breaking, and Pt-Pt bond breaking/reformation in cathode potential-jump processes and the rate constants of those transformations in the surface reaction sequences on the cathode electrocatalysts by in situ time-resolved X-ray absorption fine structure (XAFS) method. Spatially heterogeneous issue and mechanism for the Pt oxidation and degradation of Pt/C cathode electrocatalyst layers in PEFCs under the operating conditions, which should be uncovered for development of next-generation PEFCs, were also characterized by a scanning nano-XAFS mapping method and a laminography-XAFS method, respectively for 2D and 3D visualizations of Pt chemical species in Pt/C cathode electrocatalyst layers. These XAFS techniques provided new insights into critical issues affecting the performance and property of practical PEFCs under the operating conditions. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Selective catalysis is critical for the development of green chemical processes, and natural enzymes that possess specialized three-dimensional reaction pockets with catalytically active sites represent the most sophisticated systems for selective catalysis. A reaction space in an enzyme consists of an active metal center, functional groups for molecular recognition (such as amino acids), and a surrounding protein matrix to prepare the reaction pocket. The artificial design of such an integrated catalytic unit in a non-enzymatic system remains challenging. Molecular imprinting of a supported metal complex provides a promising approach for shape-selective catalysis. In this process, an imprinted cavity with a shape matched to a template molecule is created in a polymer matrix with a catalytically active metal site. [ABSTRACT FROM AUTHOR]

Abstract: Density functional theory calculations for NO adsorption and NO–CO reaction on a Co2+-dimer/γ-Al2O3(110) model catalyst were conducted to understand two new aspects of the increases in the amount and reduction rate of adsorbed NO by gas phase CO molecules which are undetectable at the Co2+-ensemble/γ-Al2O3 catalyst surface. Three kinds of dinitrosyl adsorbates were found and assigned to normal gem-dinitrosyl species (gem-dinitosyl I and II) and an unique cis-(NO)2 dimeric species. The gem-dinitrosyl II with a reconstructed structure involving Co–Osurf cleavage was considered as stable species experimentally observed, which is responsible for the spectator CO-promoted NO adsorption. We also found that the cis-(NO)2 dimeric species specific for the Co2+-ensemble structure possesses a much higher reactivity than the gem-dinitrosyl species, enabling the facile reaction with CO that is very weakly trapped at the surface. In the cis-(NO)2 dimeric species two adsorbed NO molecules on two adjacent Co2+ sites interact with each other due to the opposed orientation of the unoccupied d orbitals of the two Co2+, resulting in easy formation of a N–N bond through the 2π*–2π* hybridization. The NO adsorbates modify and activate the surface (Co2+ sites) to make pseudo-compounds (intermediates) with CO at the Co2+ sites in such a way that CO is not detected at the surface. The potential energy surface for the NO–CO reaction is presented and the transition states and intermediates are discussed. [Copyright &y& Elsevier]

We have prepared a novel Ru-mononer complex supported on a SiO2 surface by using a Ru-monomer complex precursor with a p-cymene ligand, which was found to be highly active for the selective oxidation of aldehydes and the epoxidation of alkenes using O2. The structure of the supported Ru catalyst was characterized by means of FT-lR, solid-state NMR, diffuse-reflectance UV/vis, XPS, Ru K-edge EXAFS, and DFT calculations, which demonstrated the formation of isolatedly located, unsaturated Ru centers behind a p-cymene ligand of the Ru-complex precursor. The site-isolated Ru-monomer complex on SiO2 achieved tremendous TONs (turnover numbers) for the selective oxidation of aldehydes and alkenes; e.g. TONs of 38,800,000 for selective isobutyraldehyde (IBA) oxidation and 2,100,000 for trans-stilbene epoxidation at ambient temperature, which are among the highest TONs in metal-complex catalyzes to our knowledge. We also found that the IBA sole oxidation with an activation energy of 48 kJ mol-1 much more facile than the trans-stilbene epoxidation with an activation energy of 99 kJ mol-1 was completely suppressed by the coexistence of trans-stilbene. The switchover of the selective oxidation pathways from the IBA oxidation to the trans-stilbene epoxidation was explained in terms of energy profiles for the alternative selective oxidation pathways, resulting in the preferential coordination of trans-stilbene to the Ru-complex at the surface. This aspect gives an insight into the origin of the efficient catalysis for selective epoxidation of alkenes with IBA/O2. [ABSTRACT FROM AUTHOR]

Abstract: This article illustrates two types of organofunctionalized heterogeneous catalysts for variety of organic carbon–carbon bond-forming reactions, summarizing our previous reports and also presenting new data. Organic amines with an alkoxysilane moiety were immobilized on inorganic silica-alumina surfaces (SA-NR2) by simple silane-coupling reactions between the silica-alumina surface (SA) and the alkoxysilane. This SA-NR2 acted as acid–base bifunctional heterogeneous catalysts for carbon–carbon bond-forming reactions, such as cyano-ethoxycarbonylation, Michael reaction of nitriles, and nitro-aldol reaction. These reactions did not occur with either SA or homogeneous amine compounds. In addition, the mixture of SA and homogeneous amine showed low catalytic activity due to undesirable acid–base neutralization reaction. Achiral organic silane-coupling reagents with a variety of functional groups were also immobilized on a SiO2 surface that had been immobilized with chiral bis(oxazoline) (BOX), to which Cu ions were coordinated to make chiral Cu–BOX complexes on the SiO2 surface. The SiO2-supported Cu–BOX complex catalyst functionalized with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels–Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The organofunctionalized catalysts showed much better performances for the C–C bond-forming reactions compared to the corresponding homogeneous systems. The heterogeneous catalysts thus obtained were characterized by solid-state 13C and 29Si MAS NMR, FT-IR, UV/vis, XAFS, ESR, XRF, and elemental analysis. [Copyright &y& Elsevier]

This article illustrates how bifunctional catalyst surfaces are created by modifying oxide surfaces with organic functional groups and/or with metal complexes, summarizing our previous reports and also presenting new data, which provide a new class of catalytic materials with a high complexity for selective catalysis including C–C coupling, hydroformylation, and asymmetric reactions. The catalyst surfaces are characterized by in situ physical analysis techniques such as time-resolved XAFS, FT-IR, solid-state MAS NMR and so on. [ABSTRACT FROM AUTHOR]

Abstract: A series of immobilized metal ion-containing ionic liquids on silica surfaces (ImmM_IL) were prepared and characterized by EXAFS, UV–vis, TGA, and elemental analysis. The prepared ImmCu2+_IL was found to be more active than unsupported [Bmim]2CuCl4 ionic liquid and reusable for Kharasch addition reaction between CCl4 and styrene. The prepared ImmPd2+_IL was active and reusable for Suzuki cross-coupling between phenylboronic acid and arylhalide. Throughout this study the present catalyst preparation method was confirmed to give efficient and reusable catalysts. [Copyright &y& Elsevier]

Abstract: The recent advanced design of surface reaction spaces for heterogeneous selective catalysis in molecular-nano scales is reviewed, focusing on our recent challenges and also presenting new data. Supported metal complexes on oxide surfaces often exhibit tremendous catalytic properties based on their unique coordination structures created at the surfaces. Novel active reaction spaces can be designed by coordination regulation on central metals, chemical interaction at metal–surface interface, and three-dimensional architectures constructed at surfaces. Such molecularly organized surfaces possess advantageous properties of both homogeneous and heterogeneous catalyst systems and provide great opportunities for the tailor-made design of highly selective catalysis for various kinds of catalytic chemical syntheses. [Copyright &y& Elsevier]

Abstract: A catalytic aspect, ‘surface catalytic NO reactions assisted by gas phase CO molecules’ on a Co2+-ensemble/γ-Al2O3 catalyst, was elucidated by successive density functional theory (DFT) calculations on a Co2+-dimer/γ-Al2O3 model surface. Unique cis-(NO)2 dimeric species formed due to a specific alignment of the unoccupied orbitals on the Co2+-dimer, whose vibrational frequencies were almost identical to those for conventional gem-dinitrosyl species. The cis-(NO)2 species showed much higher reactivity with CO than the gem-dinitrosyl species, through the 2π∗–2π∗ bonding between the two NO adsorbates. Detailed DFT calculations for the reaction pathways indicated an Eley–Rideal mechanism with an unusually large reactive cross-section. [Copyright &y& Elsevier]

TAP (temporal analysis of products) technique was used to clarify the controversial mechanism for low-temperature CO oxidation on supported Au catalysts involving unidentified moisture effects on the performances. The unique TAP transient technique, along the use of a specially prepared, highly active Au/Ti(OH) catalyst, provided the information and characterization of each elementary step involving weak and reversible CO adsorption, strong and molecular O2 adsorption, and their surface reaction, which are suppressed by the coexistence of water vapor. [ABSTRACT FROM AUTHOR]

Abstract: The effect of moisture on the behavior of the active supported gold catalysts developed by us, Au/Ti(OH)∗ 4 (I) and Au/Fe(OH)∗ 3 (II), during CO activation and CO oxidation in the temperature range 298–473 K was investigated by the temporal analysis of products (TAP) technique. The oxidation reaction over the Au/Ti(OH)∗ 4 catalyst was totally suppressed by the presence of water, independent of the water content of 200 and 1000 ppm, the carbon monoxide-to-oxygen ratio, and the temperature. In contrast, the presence of water vapors showed no effect on CO oxidation over the Au/Fe(OH)∗ 3 catalyst. For both catalysts, the carbon monoxide adsorption feature was unalterable by the presence of water, namely CO molecules reversibly adsorbed on the catalyst surface, but the amount of CO adsorbed decreased by increasing water content. When a reaction mixture at a 1:1 ratio of CO to O2 was pulsed on the catalyst in the absence of water, the CO response curve showed two peaks, whereas in the presence of water, the TAP response curve showed only one peak. At a 1:3 CO-to-O2 ratio, the CO response curve showed only one peak, which shifted to a shorter time and narrowed in the absence of water. The shift was more pronounced on catalyst (II). The TAP experiments provided indirect evidence that CO and water adsorbed together (CO weakly and water strongly) and water blocked [irreversibly for Au/Ti(OH)∗ 4 and reversibly for Au/Fe(OH)∗ 3], the adsorption sites for oxygen. [Copyright &y& Elsevier]

Abstract: Novel SiO2-supported chiral Cu-bis(oxazoline) (BOX) complexes for asymmetric Diels–Alder reactions were prepared by combining metal-complex immobilization with surface functionalization using achiral silane-coupling reagents on SiO2. We found that the surface functionalization of a SiO2-supported Cu-BOX catalyst with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels–Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The Cu-BOX complexes on bare and functionalized SiO2 surfaces were characterized by XAFS, ESR, FT-IR, UV/vis, and 29Si solid-state MAS NMR. The large increase in enantioselectivity by achiral surface species without chiral center may be due to a glue effect, creating a new chiral ensemble structure at the surface. [Copyright &y& Elsevier]

Abstract: We have prepared novel metal-ensemble catalysts by chemical attachment of metal-complex precursors, N-interstitial Re10 cluster supported on HZSM-5 and chiral self-dimerized V-dimer on SiO2, which are active and highly selective for selective oxidation with molecular oxygen. The Re10(N)2/HZSM-5 catalyst exhibited 87.7% (steady-state reaction) and 93.9% (pulse reaction) selectivity for direct phenol synthesis from benzene with molecular oxygen. The structures of active metal species were characterized by EXAFS, TPD and DFT calculations. The chiral self-dimerized V-dimer catalyst was found to be the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol with molecular oxygen, which exhibited 100% selectivity and 90% enantioselectivity. [Copyright &y& Elsevier]

Abstract: We have found that a surfactant cetyltrimethylammonium bromide promoted the formation of metallic Cu nanoparticles on several metal oxides under hydrothermal synthesis conditions without any additive reductants. The Cu nanoclusters and oxide supports were characterized by means of XRD, XRF, XPS, XAFS, BET, SEM, and TEM. We have also found that the supported metallic Cu nanoparticles were active for the selective dehydrogenation of methanol to produce formaldehyde and hydrogen with 100% H2 selectivity. [Copyright &y& Elsevier]

This review illustrates how catalytically active molecular structures are created on oxide surfaces by attachment of metal complexes with subsequent structural transformation and molecular imprinting on the surfaces. Also discussed is how the designed surfaces are characterized in situ by physical techniques including conventional and time-resolved X-ray absorption fine structure. The structural transformation and molecular imprinting for attached metal complexes can provide a new class of catalytic materials with a high complexity for selective catalysis including shape-selective and asymmetric catalysis. [ABSTRACT FROM AUTHOR]

A new size- and shape-selective Rh-dimer catalyst was designed by combination of a metal-complex-attaching method and a molecular-imprinting method on an Ox.50 surface. Coordinatively unsaturated, air-stable Rh dimers with a Rh–Rh bond of 0.268 nm were prepared in 0.74-nm micropores of SiO2-matrix overlayers on the Ox.50 silica surface by attaching a Rh2Cl2(CO)4 precursor on the surface (Rh2Cl2(CO)4/SiO2), followed by coordination of template ligands P(OCH3)3 to the attached Rh species (Rhsup catalyst), and then by surface imprinting of the template with SiO2-matrix overlayers formed by hydrolysis–polymerization of Si(OCH3)4 (Rhimp catalyst). The Rh dimers, micropores, and SiO2-matrix overlayers in the molecular-imprinting Rhimp catalyst were characterized by EXAFS, BET analysis, and 29Si solid-state MAS NMR, respectively. It was found that activity of the Rhsup catalyst for hydrogenation of alkenes was promoted remarkably (35–51 times) after the imprinting. The alkene hydrogenation proceeded on the imprinted Rh dimers with a monohydride without any breaking of the Rh–Rh bond. Size and shape selectivities of the molecular-imprinting Rhimp catalyst were examined by measuring the hydrogenation rates of eight alkenes of different sizes and shapes. It was also found that the Rhimp catalyst exhibited not only high activity and stability but also size and shape selectivities for the alkene molecules, probably due to a template-size cavity, created behind the removed template ligand, being used as a reaction site. Activation energies and activation entropies for the hydrogenation of large and branched alkenes were much smaller than those for small alkenes, which implies a shift in the rate-determining step in the reaction sequence for alkene hydrogenation. The performance of the molecular-imprinting Rh-dimer catalyst is discussed from structural and kinetic viewpoints. [Copyright &y& Elsevier]

Dynamic M/P invertible helicity was successfully induced at a SiO2 surface immobilized with a dynamic helical trinuclear cobalt complex, [LCo3(NHMe2)6](OTf)3, using chiral ((R) or (S))-1-phenylethylamine. Solid-state CD spectra and theoretical calculations suggested that the fixation of the M/P helical complex on the surface via coordination interactions was the key factor of the induced chirality at the surface. [ABSTRACT FROM AUTHOR]

A non‐solvated alkyl‐substituted Al(I) anion dimer was synthesized by a reduction of haloalumane precursor using a mechanochemical method. The crystallographic and theoretical analysis revealed its structure and electronic properties. Experimental XPS analysis of the Al(I) anions with reference compounds revealed the lower Al 2p binding energy corresponds to the lower oxidation state of Al species. It should be emphasized that the experimentally obtained XPS binding energies were reproduced by delta SCF calculations and were linearly correlated with NPA charges and 2p orbital energies. [ABSTRACT FROM AUTHOR]

Two transition‐metal atoms bridged by hydrides may represent a useful structural motif for N2 activation by molecular complexes and the enzyme active site. In this study, dinuclear MoIV‐FeII complexes with bridging hydrides, CpRMo(PMe3)(H)(μ‐H)3FeCp* (2 a; CpR=Cp*=C5Me5, 2 b; CpR=C5Me4H), were synthesized via deprotonation of CpRMo(PMe3)H5 (1 a; CpR=Cp*, 1 b; CpR=C5Me4H) by Cp*FeN(SiMe3)2, and they were characterized by spectroscopy and crystallography. These Mo−Fe complexes reveal the shortest Mo−Fe distances ever reported (2.4005(3) Å for 2 a and 2.3952(3) Å for 2 b), and the Mo−Fe interactions were analyzed by computational studies. Removal of the terminal Mo−H hydride in 2 a–2 b by [Ph3C]+ in THF led to the formation of cationic THF adducts [CpRMo(PMe3)(THF)(μ‐H)3FeCp*]+ (3 a; CpR=Cp*, 3 b; CpR=C5Me4H). Further reaction of 3 a with LiPPh2 gave rise to a phosphido‐bridged complex Cp*Mo(PMe3)(μ‐H)(μ‐PPh2)FeCp* (4). A series of Mo−Fe complexes were subjected to catalytic silylation of N2 in the presence of Na and Me3SiCl, furnishing up to 129±20 equiv of N(SiMe3)3 per molecule of 2 b. Mechanism of the catalytic cycle was analyzed by DFT calculations. [ABSTRACT FROM AUTHOR]

The article presents a study which discusses the immobilization of organic primary amines in acidic montmorillonite interlayers, which is the primary material that make one-pot acid-base reaction possible. It mentions that immobilizing organic bases on solid acid surfaces allows efficient bifunctional catalysis without neutralization between surface acid sites. It relates that further study on the behavior of coexisting acids will offer possibilities of application of one-pot reaction sequences.

The article presents a novel silica-alumina (SA)-supported organic amines (SA-NR2) as nanostructured heterogeneous catalysts. According to the authors, the promising adjacent position of acid and base sites on the SA-NR2 realized high catalytic activity for a variety of organic transformations. The advanced solid-state NMR analyses showed that the basic amine groups were immobilized at the neighboring position of the surface acid site without strong acid-base interaction.

For devices encountering long‐term stability challenges, a precise evaluation of degradation is of paramount importance. However, methods for comprehensively elucidating the degradation mechanisms in devices, particularly those undergoing dynamic chemical and mechanical changes during operation, such as batteries, are limited. Here, a method is presented using operando computed tomography combined with X‐ray absorption near‐edge structure spectroscopy (CT‐XANES) that can directly track the evolution of the 3D distribution of the local capacity loss in battery electrodes during (dis)charge cycles, thereby enabling a five‐dimensional (the 3D spatial coordinates, time, and chemical state) analysis of the degradation. This paper demonstrates that the method can quantify the spatiotemporal dynamics of the local capacity degradation within an electrode during cycling, which has been truncated by existing bulk techniques, and correlate it with the overall electrode performance degradation. Furthermore, the method demonstrates its capability to uncover the correlation among observed local capacity degradation within electrodes, reaction history during past (dis)charge cycles, and electrode microstructure. The method thus provides critical insights into the identification of degradation factors that are not available through existing methods, and therefore, will contribute to the development of batteries with long‐term stability. [ABSTRACT FROM AUTHOR]

The hydride-supported [Mo2Fe2] cluster complex {Cp*Mo(PMe3)}2{FeN(SiMe3)2}2(H)8 ( 2 a; Cp*=η5-C5Me5) and its [Mo2Mn2] congener 2 b were synthesized from the reactions of Cp*Mo(PMe3)(H)5 ( 1) with M{N(SiMe3)2}2 (M=Fe, Mn). The amide-to-thiolate ligand-exchange reactions of complex 2 a with bulky thiol reagents (HSR; R=2,4,6- iPr3C6H2 (Tip), 2,6-(SiMe3)2C6H3 (Btp)) furnished the corresponding hydride-supported [Mo2Fe2](SR)2 cluster complexes. The [Mo2Fe2] clusters served as catalyst precursors for the reductive silylation of N2 and yielded ≈65-69 equivalents of N(SiMe3)3 relative to the [Mo2Fe2] clusters. Treatment of complexes 2 a and b with an excess of CN tBu resulted in the formation of dinuclear Mo−Fe and Mo−Mn complexes, which indicated that the [Mo2M2] cores (M=Fe, Mn) split into two dinuclear species upon accommodation of substrates. [ABSTRACT FROM AUTHOR]

Acid–base bifunctional catalysts were prepared by immobilization of basic amines on acidic silica–alumina (SA) surfaces. Silane-coupling reagents with various amino-functional groups, such as primary, secondary, and tertiary alkylamines, alkyldiamine, and dialkylaminopyridine, were examined as anchoring reagents for the amines in the preparation of catalysts. The obtained immobilized catalysts (SA–NR′R′′) were characterized by solid-state 13C and 29Si MAS NMR and elemental analysis. The catalytic activity of tertiary alkylamines for Michael reactions increased dramatically by the immobilization on silica–alumina, whereas a homogeneous tertiary amine scarcely promoted the reaction. Regarding the kind of amines, the dialkylaminopyridine immobilized silica–alumina with low Al content (SAL) showed the highest catalytic performance among the amine immobilized catalysts. The solid-state 13C NMR analysis revealed the interaction between the nitrogen atom on pyridine ring and a surface strong acid site of the silica–alumina support. [ABSTRACT FROM AUTHOR]

Abstract: Bis(1-n-butyl-3-methyl-imidazolium)tetrachloronickelate ([Bmim]2[NiCl4]), which is a nickel ion-containing ionic liquid, and immobilized nickel ion-containing ionic liquid (ImmNi2+_IL) on silica surface were prepared and applied as new catalysts for Suzuki cross-coupling reactions between aryl chlorides and arylboronic acids. It was found that pretreatment of the catalysts and the addition of triphenylphosphine to the reaction system greatly promoted the reactions. Before the addition of substrates, [Bmim]2[NiCl4] should be treated with K3PO4 in dioxane at a refluxing temperature for 1 h, and ImmNi2+_IL should be treated with NaOtBu in dioxane at room temperature for 30 min. An active precursor for the catalytic reactions was found to be a Ni carbene species formed by pretreatment with the bases as characterized by NMR and EXAFS. Reusability was confirmed for ImmNi2+_IL. [Copyright &y& Elsevier]

We have developed a new Pt–Fe/mordenite (Pt–Fe/M) catalyst which shows remarkably high activity and selectivity for the oxidation of CO in H2-rich gas compared with Pt/M. In the present work, to understand the role and structure of Pt and Fe in the Pt–Fe/M catalyst, the states of metallic components in ion-exchanged, H2 pre-treated and post-PROX (preferential oxidation of CO) samples have been studied by means of XAFS. It was confirmed that Pt forms the metallic clusters after H2 pretreatment or the PROX experiment, whereas a large part of Fe exists as oxides even after the H2 treatment. At post-analysis of the catalysts used for the PROX experiment, an increase in coordination number of Fe–O was observed. Pt clusters in the Pt–Fe(2:1 weight ratio)/M catalyst, which showed the highest PROX performance, were found to have a different electronic structure from the other catalysts. Additionally, preferential CO adsorption onto Pt sites at Pt–Fe/M was clearly demonstrated by infrared spectroscopy analysis in a stream of 1% CO containing H2. Based on these results, the superior PROX mechanism was discussed. [ABSTRACT FROM AUTHOR]

Ultrafine bimetallic Pt–Ni nanoparticles, which catalyze the oxygen reduction reaction (ORR) efficiently, were successfully prepared in hollow porous carbon spheres (HPCSs) under the assistance of organic molecules. 2,2′-Dipyridylamine (dpa) was found to be most effective in preparing homogeneous small Pt–Ni nanoparticles (2.0 ± 0.4 nm) without the phase separation of Pt and Ni during synthesis, and the assistance of the organic molecules was investigated for the alloy nanoparticle formation. The Pt–Ni nanoparticle/HPCS catalyst synthesized in the presence of dpa exhibited remarkable electrochemical performance in the ORR showing a high mass activity of 3.25 ± 0.14 A mg−1Pt at 0.9 VRHE (13.5-fold higher relative to a commercial Pt/C catalyst), a large electrochemical surface area of 105 ± 8 m2 g−1Pt, and high durability. After 60 000 cycles of accelerated durability testing, the mass activity was still 12.3 times higher than that of the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Rate enhancement of the selective oxidation of hexoses was achieved on an ethynylpyridine (EPy)-functionalized Pt/Al2O3 catalyst. Host–guest interaction between the EPy ligand and a hexose sugar reactant produced a complex with induced chirality on the catalyst surface. [ABSTRACT FROM AUTHOR]

• The molecularly imprinted catalysts now targets a wide range of catalytic reactions. • Imprinted organic polymer catalyst controlling aldol reaction by outer stimuli. • Imprinted porous aromatic frameworks for the most efficient hydrolysis. • Imprinted micelle nanoparticle catalysts for asymmetric aldol reaction. • Surface imprinted catalysts for shape/chemoselective cross-coupling and epoxidation. Molecular imprinting has been developed to prepare space mimicking the shape of molecule in material, and it has been applied to sensing, adsorption, catalysis, etc. Molecularly imprinted catalysts show unique performances to regulate activity and selectivity of catalytic reactions, including organic reactions. Many ideas and materials have been introduced to the field, and this digest review highlights some of the recent developments by describing several remarkable achievements in this field. [ABSTRACT FROM AUTHOR]

Hydride-bridged transition metal complexes have been found to serve as suitable precursors for the activation of small molecules without the use of reducing agents. In this study, we synthesized a dinuclear Mo2H8 complex supported by bulky C5H2tBu3 (Cp‡) ligands, Cp‡2Mo2H8 (1), from the reaction of Cp‡MoCl4 with KC8 under H2. The hydrides of complex 1 can be replaced with benzene at 60 °C to afford a μ-benzene complex Cp‡2Mo2H2(μ-C6H6) (2). [ABSTRACT FROM AUTHOR]

A pincer‐iridium complex bearing a Lewis‐base‐free X‐type alumanyl ligand has been synthesized. X‐ray diffraction, NMR and IR spectroscopy, as well as XANES analysis confirmed its tetrahydrido‐IrV structure and Lewis acidity at the Al center as supported by DFT calculations. The resulting complex was applied as a catalyst for the transfer dehydrogenation of cyclooctane. [ABSTRACT FROM AUTHOR]

A pincer‐iridium complex bearing a Lewis‐base‐free X‐type alumanyl ligand has been synthesized. X‐ray diffraction, NMR and IR spectroscopy, as well as XANES analysis confirmed its tetrahydrido‐IrV structure and Lewis acidity at the Al center as supported by DFT calculations. The resulting complex was applied as a catalyst for the transfer dehydrogenation of cyclooctane. [ABSTRACT FROM AUTHOR]

Three‐dimensional imaging using X‐ray as a probe is state‐of‐the‐art for the characterization of heterogeneous materials. In addition to simple imaging of sample morphology, imaging of elemental distribution and chemical states provides advanced maps of key structural parameters of functional materials. The combination of X‐ray absorption fine structure (XAFS) spectroscopy and three‐dimensional imaging such as computed tomography (CT) can visualize the three‐dimensional distribution of target elements, their valence states, and local structures in a non‐destructive manner. In this personal account, our recent results on the three‐dimensional XAFS imaging for Pt cathode catalysts in the membrane electrode assembly (MEA) of polymer electrolyte fuel cell (PEFC) are introduced. The distribution and chemical states of Pt cathode catalysts in MEAs remarkably change under PEFC operating conditions, and the 3D XAFS imaging revealed essential events in PEFC MEAs. [ABSTRACT FROM AUTHOR]

Size-controlled Pt nanoparticles were prepared on multi-wall carbon nanotubes (MWCNTs) decorated with polypyrrole matrix overlayers and exhibited superior oxygen reduction reaction (ORR) performance as electrocatalysts. The copolymerization of a new Pt4-pyrrole complex and pyrrole monomer in the presence of MWCNTs produced size-controlled Pt nanoparticles with diameters of 1.5 ± 0.5 nm. The present size-controlled Pt nanoparticles showed better durability than non-regulated Pt nanoparticles without polypyrrole and a commercial Pt/C catalyst during the ORR at the fuel cell cathode without substantial aggregation of the size-controlled Pt nanoparticles. [ABSTRACT FROM AUTHOR]

The preparation of water‐soluble, N‐heterocyclic‐carbene‐stabilized Au–Pd alloy nanoparticles by a straightforward ligand exchange process is presented. Extensive analysis revealed excellent size retention and stability over years in water. The alloy nanoparticles were applied as biomimetic catalysts for aerobic oxidation of d‐glucose, for which monometallic Au and Pd nanoparticles showed no or negligible activity. The alloy nanoparticles were further applied as titania‐supported heterogeneous catalysts for the mild hydrogenation of nitroarenes and the semihydrogenation of 1,2‐diphenylacetylene with a solvent‐dependent selectivity switch between E‐ and Z‐stilbene. It's all about the mix! The preparation of water‐soluble, N‐heterocyclic‐carbene‐stabilized Au–Pd alloy nanoparticles is presented. The particles were stable over years and were used as biomimetic catalysts in water or as heterogeneous catalysts in hydrogenation reactions. [ABSTRACT FROM AUTHOR]

A synthetic protocol was developed for a series of cubane‐type [Mo3S4M] clusters that incorporate halides of first‐row transition metals (M) from Groups 4–10. This protocol is based on the anionic cluster platform [Cp*3Mo3S4]− ([1]−; Cp*=η5‐C5Me5), which crystallizes when K(18‐crown‐6) is used as the counter cation. Treatment of in situ‐generated [1]− with such transition‐metal halides led to the formation of [Mo3S4M] clusters, in which the M/halide ratio gradually changes from 1:2 to 1:1.5 and to 1:1, when moving from early to late transition metals. This trend suggests a tendency for early transition metals to tolerate higher oxidation states and adopt larger ionic radii relative to late transition metals. The properties of the [Mo3S4Fe] cluster 6 a were investigated in detail by using 57Fe Mössbauer spectroscopy and computational methods. Cubic clusters: A synthetic protocol was developed for a series of cubane‐type [Mo3S4M] clusters, based on the anionic cluster platform [Cp*3Mo3S4]−, which incorporate halides of first‐row transition metals (M) from Group 4–10. The M/halide ratio gradually increases from 1:2 to 1:1.5 and to 1:1 upon moving from early to late transition metals. [ABSTRACT FROM AUTHOR]

A new molecularly imprinted Ru–porphyrin complex catalyst on a SiO2 support was designed, prepared, and characterized in a step-by-step manner for the C5=C6 epoxidation of cholesterol derivatives. High chemoselectivity for the C5=C6 epoxidation of cholesterol derivatives without protecting the 3-position OH group and other oxidizable functional groups was achieved on the molecularly imprinted catalyst. [ABSTRACT FROM AUTHOR]

Ru nanoparticle catalysts were prepared from Ru12–metalloporphyrin complex precursors containing 3d transition-metal atoms attached to SiO2 surfaces. The single 3d metal atoms at the central position of the Ru12–metalloporphyrin complex precursors exerted a significant influence on the structures and hydrogenation performance of the Ru nanoparticles on the SiO2 surfaces. The Ru12–Cu–porphyrin complex afforded positively charged Ru nanoparticles, which would provide high activity toward aromatic hydrogenation. [ABSTRACT FROM AUTHOR]

Abstract: The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce2Zr2Ox (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2Zr2Ox particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Abstract: The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce2Zr2Ox (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2Zr2Ox particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized in a practical polymer electrolyte fuel cell (PEFC) under fuel-cell operating conditions. Operando 3D computed-tomography imaging with X-ray absorption near edge structure (XANES) spectroscopy (CT-XANES) clearly revealed the heterogeneous migration and degradation of Pt cathode catalyst in an MEA during accelerated degradation test (ADT) of PEFC. The degradative Pt migration proceeded over the entire cathode catalyst layer and spread to MEA depth direction into the Nafion membrane. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized in a practical polymer electrolyte fuel cell (PEFC) under fuel-cell operating conditions. Operando 3D computed-tomography imaging with X-ray absorption near edge structure (XANES) spectroscopy (CT-XANES) clearly revealed the heterogeneous migration and degradation of Pt cathode catalyst in an MEA during accelerated degradation test (ADT) of PEFC. The degradative Pt migration proceeded over the entire cathode catalyst layer and spread to MEA depth direction into the Nafion membrane. [ABSTRACT FROM AUTHOR]