Abstract: Methanol, an important chemical, fuel additive, and precursor for clean fuels, is produced by hydrogenation of carbon oxides over Cu-based catalysts. Despite the technological maturity of this process, the understanding of this apparently simple reaction is still incomplete with regard to the reaction mechanism and the active sites. Regarding the latter, recent progress has shown that stepped and ZnOx-decorated Cu surfaces are crucial for the performance of industrial catalysts. Herein, we integrate this insight with additional experiments into a full microkinetic description of methanol synthesis. In particular, we show how the presence or absence of the Zn promoter dramatically changes not only the activity, but unexpectedly the reaction mechanism itself. The Janus-faced character of Cu with two different sites for methanol synthesis, Zn-promoted and unpromoted, resolves the long-standing controversy regarding the Cu/Zn synergy and adds methanol synthesis to the few major industrial catalytic processes that are described on an atomic level.

Abstract: Single-atom catalysts (SACs) with individual and isolated metal atoms anchored to supports can act as active centers. Single-atom catalysis is powerful and attractive because SACs have demonstrated distinguishing performances, such as drastic cost-reduction, notable catalytic activity, and selectivity. Herein, we firstly introduce SAC, including the concept and some key issues in synthesis and catalysis. Then, the power of single-atom catalysis is highlighted and the most recent advances are summarized. It is very encouraging that in recent years our understanding of SACs has increased, owing to substantial studies regarding sample preparation, characterization, evaluation, and also mechanistic interpretation. On the other hand, great challenges still remain for SACs.

Abstract: Novel biomass-derived porous carbons are attractive candidates for the preparation of carbon-supported catalysts with a wide range of catalytic applications. Such carbonaceous catalysts are environmentally benign and could provide a cost-competitive advantage as compared to existing heterogeneous catalysts. Tunable surface properties of carbon materials and excellent physical properties (e.g., hydrophobicity, chemically inert nature, etc.) are compatible with diverse catalysis reactions including organic transformations, as well as electro- and photochemical processes in aqueous solutions. This contribution provides an overview on the utilization of different biomass feedstocks and/or biomass-derived precursors for the synthesis of carbonaceous materials to design advanced catalytic systems and their emerging applications in catalysis.

Abstract: The recent development of nanostructured electrocatalysts for CO2 reduction has attracted much attention because they exhibit unique properties compared to their bulk counterparts. In this minireview, the latest studies on electrocatalytic CO2 reduction with a focus on the advances of nanostructured metallic electrocatalysts are reviewed and discussed. The distinct catalytic properties and potential challenges of nanostructured electrocatalysts are summarized. The behavior of nanosized catalysts in ionic liquid electrolytes is also discussed. Ideas for the design of next-generation electrocatalysts by taking the advantages of nanostructured materials are proposed.

Abstract: Since their introduction in 2004, deep eutectic solvents (DESs) have attracted interest in different fields of chemistry. In the case of biomass, DESs are particularly interesting, not only because of their low cost and biodegradability, but also due to their unique property to interact with hydrogen-bond donors such as renewably sourced polyols or carboxylic acids. Through selected examples, we report the contribution of DESs for the dissolution of biomass, the extraction/purification of bio-derived chemicals, and the conversion of carbohydrates to furanic derivatives. In all examples, we discuss how the DES can impact the selectivity of a chemical process and the limitations associated with the use of DES. In particular, impact of the DES viscosity on extraction, the recovery and recycling of DES, and the stabilization of chemical intermediates in DES are among the key aspects that are discussed.

Abstract: X‐ray photoelectron spectroscopy (XPS) is a widely used technique for characterizing the chemical and electronic properties of highly ordered carbon nanostructures, such as carbon nanotubes and graphene. However, the analysis of XPS data—in particular the C 1s region—can be complex, impeding a straightforward evaluation of the data. In this work, an overview of extrinsic and intrinsic effects that influence the C 1s XPS spectra—for example, photon broadening or carbon–catalyst interaction—of various graphitic samples is presented. Controlled manipulation of such samples is performed by annealing, sputtering, and oxygen functionalization to identify different CC bonding states and assess the impact of the manipulations on spectral line shapes and their binding energy positions. With high‐resolution XPS and XPS depth profiling, the spectral components arising from disordered carbon and surface‐defect states can be distinguished from aromatic sp2 carbon. These findings illustrate that both spectral line shapes and binding energy components must be considered in the analysis of potentially defective surfaces of carbon materials. The sp2 peak, characteristic of aromatic carbon, features a strong asymmetry that changes with the curvature of the sample surface and, thus, cannot be neglected in spectral analysis. The applied deconvolution strategy may provide a simple guideline to obtaining high‐quality fits to experimental data on the basis of a careful evaluation of experimental conditions, sample properties, and the limits of the fit procedure.

Abstract: A series of alumina-supported Ni catalysts were prepared to examine their activity and carbon deposition during dry reforming of methane (DRM). With an increase in the final calcination temperature to T=900 °C to form exclusively NiAl2O4, a catalyst with strong metal–support interactions was obtained. During a long-term DRM reaction (of about t=100 h) at T=700 °C and with CH4/CO2=1:1, reduced Ni (from NiAl2O4) showed a high resistance to sintering and coking. The DRM kinetics behaviors of the catalysts calcined at different temperatures were also investigated. Carbon growth models were proposed to rationalize the different carbon morphologies observed on the catalysts.

Abstract: Magnetic nanoparticles have emerged recently as an alternative for the easy separation of nanosized catalysts from reaction mixtures by employing an external magnetic field. These magnetic nanoparticles have been used as supports for catalysts and/or as part of an active catalytic site. Herein, special attention is given to identify the main synthetic steps required to develop both precious‐ and nonprecious‐metal‐catalyzed CC and CX coupling reactions by using magnetically separable catalysts.

Abstract: Owing to extensive industrial revolutions, the harvesting of sunlight for environmental remediation has attracted extensive attention and a number of potential photocatalysts have been reported. These photocatalysts were prepared according to their effectiveness under various light irradiations, that is, from UV/Vis to near-infrared (NIR) regions and finally to full solar light spectrum. This review briefly summarizes recent progress in the enhancement of photocatalytic activities of prepared photocatalysts under various light irradiations. To understand the photocatalytic process, photocatalytic mechanisms and band-structure engineering are discussed in detail in this review. Moreover, various effective photocatalysts are taken as examples of the photocatalytic process under various light irradiations. Finally, the challenges and perspectives of photocatalysis under different lights irradiations are presented.

Abstract: The incorporation of cocatalysts into semiconductors is proved to be an effective approach to improving the efficiency of the photocatalytic H2 production. Noble metals such as Pt have been widely used as cocatalysts and can significantly improve the performance of photocatalytic H2 production. However, owing to the high cost and low abundance, the use of Pt in practical applications is restricted. Herein, we report two well-known 2 D layered materials, MoS2 and graphene, as highly active cocatalysts for H2 production in CdS-based photocatalytic systems. The CdS–MoS2 and CdS-MoS2–graphene nanocomposites were prepared by using a facile two-step solvothermal method, and the morphologies of CdS and MoS2 can be well controlled. The as-prepared binary CdS–MoS2 nanocomposite exhibits the enhanced visible-light photocatalytic activity for H2 production in lactic acid aqueous solution compared with a CdS–graphene nanocomposite and a conventional platinized CdS photocatalyst. Moreover, the ternary CdS–MoS2–graphene nanocomposite achieves the highest visible-light photocatalytic H2 production activity of 621.3 μmol h−1 and the apparent quantum efficiency of 54.4 % at λ=420 nm. The enhanced photocatalytic activity of the CdS–MoS2–graphene nanocomposite can be primarily attributed to the positive synergistic effect between graphene sheets and thin MoS2 nanoplates. The graphene sheets can accelerate the efficient electron transfer from CdS nanorods to the active edge sites of MoS2 nanoplates, and the nanosized MoS2 can facilitate the photogenerated electrons participating in the photocatalytic H2 production. The mechanisms for improving the photocatalytic performance of the MoS2- and/or graphene-modified CdS nanocomposites were proposed by using the electrochemical analysis and photoluminescence measurement.

Abstract: Electrocatalytic hydrogen evolution has been regarded as a promising strategy to realize efficient hydrogen production to face the energy crisis in the future. Hence, the design of hydrogen-evolving catalysts with high activity and low cost is imperative. In this Minireview article, state-of-the-art electrocatalysts for the hydrogen evolution reaction (HER) are overviewed, and the strategies for constructing ordered and disordered HER electrocatalysts are summarized in detail. By means of facet engineering, nanoscale, polymorph engineering accompanied by interface engineering, HER catalysts with an ordered structure could be optimized. For designing disordered catalysts, defect engineering, amorphization, elemental doping, and surface modification, as well as constructingan alloyed structure, could be effective to realize the beneficial modulation of active sites and electronic structure. This Minireview provides a structural perspective for the design of efficient HER electrocatalysts in the future.

Abstract: This minireview encompasses the most recent (since 2010) advancements in the field of photocatalytic hydrogen-atom transfer (HAT) processes for CH bond functionalization. The direct HAT process promoted from the excited state of a photocatalyst is limited to the classes of polyoxometalates and aromatic ketones, but alternative photocatalytic strategies have recently been devised to alleviate this shortcoming, making use of indirect HAT reactions. The applications of these two approaches in organic synthesis, including the formation of CC, as well as Chalogen, CO (CO), and CN bonds, are presented herein.

Abstract: The front cover artwork for Issue 3/2015 has been provided by a research group from the State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University. The image depicts a new strategy to construct a composite of an ionic liquid, a polyoxometalate, and a metal–organic framework. See the Full Paper itself at http://dx.doi.org/10.1002/cctc.201402800.

Abstract: Although the range of biocatalysts available for the synthesis of enantiomerically pure chiral amines continues to expand, few existing methods provide access to secondary amines. To address this shortcoming, we have over-expressed the gene for an (R)-imine reductase [(R)-IRED] from Streptomyces sp. GF3587 in Escherichia coli to create a recombinant whole-cell biocatalyst for the asymmetric reduction of prochiral imines. The (R)-IRED was screened against a panel of cyclic imines and two iminium ions and was shown to possess high catalytic activity and enantioselectivity. Preparative-scale synthesis of the alkaloid (R)-coniine (90 % yield; 99 % ee) from the imine precursor was performed on a gram-scale. A homology model of the enzyme active site, based on the structure of a closely related (R)-IRED from Streptomyces kanamyceticus, was constructed and used to identify potential amino acids as targets for mutagenesis.

Abstract: A comparative study of visible-light-responsive Bi2WO6 and oxygen-deficient Bi2WO6−x nanoplates was conducted. The formation of oxygen vacancy resulted in the band gap narrowing of oxygen-deficient Bi2WO6−x, through an elevation of both of the conduction and valence band positions. FTIR spectra revealed that much more surface hydroxyl groups have been detected after the etching process. The scavengers tests confirmed the generation of ⋅OH radicals during photochemical reaction for Bi2WO6−x, whereas no .OH radicals can be detected for pure Bi2WO6. The photocatalytic activities of optimized Bi2WO6−x on the decomposition of Rhodamine B (RhB) was three times as high as that of pure Bi2WO6. The improvement of photocatalytic activity on degradation of RhB and phenol can be ascribed to the synergistic effect of oxygen deficiency-induced band shifts, together with the large quantities of surface hydroxyl groups providing active sites for the generation of OH radicals (.OH).

Abstract: Hydroxy‐functionalized mono‐ and bisimidazolium bromides were synthesized and applied as catalysts for the cycloaddition of CO2 and epoxides to cyclic carbonates. A catalyst screening showed the influence of the number of protic hydrogen atoms at the cation for the activation of epoxides. The most active catalyst operates at very mild reaction conditions (70 °C, 0.4 MPa CO2) and can be easily recycled ten times without loss of activity.

Abstract: A highly efficient and green process for the hydrogenation of biomass‐derived levulinic acid (LA) to γ‐valerolactone (GVL) has been developed. GVL was obtained in a yield of 99.9 mol % with a turnover frequency as high as 7676 h−1 in aqueous medium by using a Ru/TiO2 catalyst under mild reaction conditions (70 °C). The strong interaction between Ru and TiO2 facilitated both the dispersion of Ru nanoparticles and the stability of the catalyst. In addition, as solvent, water participated in the hydrogenation of LA, which was confirmed by an isotope‐ labeling experiment with D (D2O). Specifically, the H atom(s) in water took part in the hydrogenation of the CO group of LA, which promoted the catalytic activity and GVL yield remarkably.

Abstract: Metal-free carbonaceous materials have attracted considerable interests as heterogeneous catalysts owing to their superior physiochemical properties over metal-based catalysts, such as low cost, no pollution, chemical and thermal stabilities, as well as readily tailorable porous structure and surface chemistry. This review article provides an overview of the fundamentals and recent advances in the field of metal-free carbon catalysts, including graphenes, carbon nanotubes, mesoporous carbons, graphitic carbon nitrides, and related composites. Special focus is placed on their controllable preparation and applications in gas phase, liquid phase, electrochemical, and photocatalytic reactions, as well as defect and surface chemistry related catalytic activities of carbon materials. Some perspectives are highlighted on the development of more efficient metal-free carbonaceous catalysts featuring high stability, low cost, optimized structures, and enhanced performance, which are the key factors to accelerate the designed preparation and commercialization of carbocatalysts.

Abstract: Selective hydrogenation and hydrogenolysis of 5‐hydroxymethylfurfural were performed with carbon nanotube‐supported bimetallic NiFe (NiFe/CNT) catalysts. The combination of Ni and Fe in an appropriate atomic ratio of Ni/Fe (2.0) significantly increased the selectivity to 2,5‐furandimethanol or 2,5‐dimethylfuran depending on the reaction temperature. The selectivities to 2,5‐furandimethanol and 2,5‐dimethylfuran were as high as 96.1 % at 383 K and 91.3 % at 473 K, respectively. The characterization results confirmed that bimetallic particles with sizes less than 7 nm were formed on the catalyst. Several key molecules related to 5‐hydroxymethylfurfural transformation were used to investigate the product distribution and reaction pathway. The results indicated that the formation of NiFe alloy species is beneficial to the selective cleavage of the CO bond. Recycling experiments showed that the catalyst can be easily separated with a magnet and reused several times without significant loss of activity.

Abstract: Electrochemical production of hydrogen, facilitated in electrolyzers, holds great promise for energy storage and solar fuel production. A bottleneck in the process is the catalysis of the oxygen evolution reaction, involving the transfer of four electrons. The challenge is that the binding energies of all reaction intermediates cannot be optimized individually. However, experimental investigations have shown that drastic improvements can be realized for manganese and cobalt-based oxides if gold is added to the surface or used as substrate. We propose an explanation for these enhancements based on a hydrogen acceptor concept. This concept comprises a stabilization of an *OOH intermediate, which effectively lowers the potential needed for breaking bonds to the surface. On this basis, we investigate the interactions between the oxides and gold by using DFT calculations. The results suggest that the oxygen evolution reaction overpotential decreases by 100–300 mV for manganese oxides and 100 mV for cobalt oxides.

Abstract: This Review discusses the structural and catalytic aspects of the recently introduced reactive metal–support interaction. This special term was coined to account for the inability of the original concept of the strong metal–support interaction to accurately describe the structural, compositional, and electronic changes frequently occurring in oxide‐supported metal particle catalysts at very high temperatures upon reduction in hydrogen, in many cases leading to intermetallic compound or substitutional alloy formation. This inaccuracy predominantly refers to the requirement of full reversibility upon oxidation and mild reduction for a “strong” metal–support interaction. A close look at the formation of oxide‐supported intermetallic compounds upon high‐temperature reduction reveals that these compounds are very common in catalysis and the situation is much more complex compared to unsupported intermetallic compounds due to the presence of the intermetallic compound–oxide interface.

Abstract: Multienzyme cascade approaches for the synthesis of optically pure molecules from simple achiral compounds are desired. Herein, a cofactor self-sufficient cascade protocol for the asymmetric amination of racemic secondary alcohols to the corresponding chiral amines was successfully constructed by employing an alcohol dehydrogenase and a newly developed amine dehydrogenase. The compatibility and the identical cofactor dependence of the two enzymes led to an ingenious in situ cofactor recycling system in the one-pot synthesis. The artificial redox-neutral cascade process allowed the transformation of racemic secondary alcohols into enantiopure amines with considerable conversions (up to 94 %) and >99 % enantiomeric excess at the expense of only ammonia; this method thus represents a concise and efficient route for the asymmetric synthesis of chiral amines.

Abstract: Transition-metal-catalyzed C H bond activation has evolved exponentially in recent years and has found a growing number of applications in practical synthesis. Major advances in this field have been made with catalysts based on noble transition metals such as Rh, Pd, Ru, and Ir. On the other hand, increasing interest in sustainable catalysis has recently encouraged chemists into the development of alternative catalysts based on earth-abundant first-row transition metals. Among such base metals, Co appears particularly attractive in light of the diversity of C H functionalization reactions catalyzed by its heavier congener, Rh, in both lowand high-valent states, as well as the similarity of Co and Rh in a variety of homogeneous catalytic reactions. Highlighted herein is the recent emergence of high-valent Cp*Co (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) catalysis for directed C H activation. Since the late 2000’s, C H activation by using Cp*Rh catalysts has undergone an explosive development. A variety of C C and C heteroatom bond-forming reactions by means of directing-group-assisted C H activation have been achieved in both oxidative and redox-neutral manners. In 2013, Matsunaga, Kanai, and co-workers disclosed a major breakthrough in the analogous Cp*Co catalysis, identifying a cationic Co complex [{Cp*Co(C6H6)}(PF6)2] (Cp*Co ) as a competent catalyst for the addition of 2-arylpyridines to N-sulfonylimines and enones (Scheme 1). Among several cationic Co–benzene complexes bearing different Cp-type ligands, Cp*Co proved to be the most efficient. In analogy to the related Cp*Rh catalysis, 6] the reaction is proposed to go through pyridyl-directed C H activation and nucleophilic addition of the resulting aryl Co species to the electrophile. Cp*Co catalysis tolerates a variety of functional groups, such as ester, ketone, hydroxy, amide, and halogen groups, and is also the case in other reactions discussed below. The scope of the addition to imines was further extended to N-pyrimidylindoles (Scheme 2). A combined use of Cp*Co and KOAc was found to result in a higher catalytic activity than that of Cp*Co alone. Initial dissociation of the benzene ligand from Cp*Co and anionic ligand exchange with KOAc generates a catalytically active Co acetate species, which could then undergo C2 metalation of the indole substrate by means of acetate-assisted C H activation. Notably, the reaction can be achieved with a catalyst loading as low as 0.5 mol %. Matsunaga, Kanai, and co-workers demonstrated a unique reactivity of the Cp*Co catalyst in the reaction of N-carbamoylindole with an internal alkyne (Scheme 3). Besides a C2-alkenylated indole, which is the only product under Cp*Rh catalysis, the Cp*Co catalyst produces a pyrroloindolone derivative through a C H alkenylation/annulation sequence. The product selectivity can be controlled by tuning the carbamoyl group and the reaction conditions. Both the reactions likely share C H metalation and alkyne insertion steps, but the driving force of the annulation pathway is ascribed to the more polarized nature of a Co C bond than that of a Rh C bond, which would facilitate intramolecular nucleophilic attack of the alkenyl Co intermediate to the carbamoyl group. In an effort to expand the scope of Cp*Co catalysis, Matsunaga, Kanai, and co-workers devised a new method for the in situ generation of a catalytically active cationic Cp*Co speScheme 1. Addition of 2-arylpyridine to N-sulfonylaldimine (right) or a,b-unsaturated ketone (left). DCE = 1,2-dichloroethane.

Abstract: The nickel‐catalyzed decomposition of formic acid to yield molecular hydrogen and the nickel‐catalyzed hydrogenation of bicarbonate as a carbon dioxide mimic have been examined. Well‐defined nickel complexes modified by a PCP‐pincer ligand, especially nickel hydride and nickel formate complexes, revealed catalytic activity with turnover numbers of up to 626 (decomposition) and 3000 (hydrogenation). Thus, a formal hydrogen storage and release cycle performed by a well‐defined nickel catalyst was accomplished.

Abstract: A template consisting of a melamine-based microporous polymer network was synthesized and utilized as a solid support to stabilize palladium nanoparticles; the resulting Pd/SNW1 material showed good catalytic activity in copper-free Sonogashira coupling in water. Various aryl iodides were efficiently coupled with arylacetylenes under very low catalyst loadings in an environmentally benign medium. Hot filtration tests confirmed the heterogeneity of the catalyst, which was reused under the optimized conditions without any significant change in its activity. This simple preparation of the catalyst, the stability of the catalyst, product selectivity, and easy recovery and regeneration indicate the possible utilization of this catalytic system in a multitude of catalyzed reactions and industrial processes.

Abstract: Sn-Beta zeolite was prepared by acid dealumination of Beta zeolite, followed by dehydration and impregnation with anhydrous SnCl4. The formation of extraframework Sn (EFSn) species was prevented by the removal of unreacted SnCl4 in a methanol washing step prior to calcination. The resulting Sn-Beta zeolites were characterized by X-ray diffraction, Ar physisorption, NMR, UV/Vis, and FTIR spectroscopy. These well-defined Lewis acid zeolites exhibit good catalytic activity and selectivity in the conversion of 1,3-dihydroxyacetone to methyl lactate. Their performance is similar to a reference Sn-Beta zeolite prepared by hydrothermal synthesis. Sn-BEA zeolites that contain EFSn species exhibit lower catalytic activity; the EFSn species also catalyze formation of byproducts. DFT calculations show that partially hydrolyzed framework Sn-OH species (open sites), rather than the tetrahedral framework Sn sites (closed sites), are the most likely candidate active sites for methyl lactate formation.

Abstract: A novel heterostructured CuO/BiFeO3 composite photocatalyst was successfully prepared through a simple combination of hydrothermal and impregnation process. CuO was uniformly deposited on the surface of BiFeO3 particles with a p–n heterojunction formed at the interface between CuO and BiFeO3. CuO/BiFeO3 heterostructured photocatalysts improved the UV/Vis spectral absorption ability, and exhibited enhanced photocatalytic activities for photodegradation of methylorange or a colorless compound (i.e., phenol) under visible light. In addition, after five recycles for the photodegradation of methylorange, CuO/BiFeO3 did not exhibit significant loss of photocatalytic activity, confirming its stability and long‐time reusability. The enhanced photocatalytic activity could be mainly ascribed to the p–n heterojunction structure between CuO and BiFeO3, which could significantly facilitate the separation and transfer of photogenerated electron–hole pairs. On the basis of the calculated energy bands, the photocatalytic mechanism was also proposed.

Abstract: Oxygen evolution and reduction offer a promising method of grid-level energy storage that could facilitate widespread adaptation of solar and wind power. However, the efficiency of these technologies is fundamentally limited by high overpotentials, which stem from correlations between adsorption energies of different reaction intermediates. We propose a scheme to circumvent these scaling relationships by defining a three-dimensional nanoscopic catalyst structure that capitalizes on different interactions between the intermediates and the catalyst owing to confinement. These nanoscopic channels reduce the theoretical overpotential for oxygen evolution on RuO2 by over 200 mV, corresponding to a 10 % increase in theoretical catalyst efficiency compared with a two-dimensional RuO2 surface. This approach may hold promise for other oxygen-evolution catalysts or, more broadly, to other reactions limited by (intermediate) adsorption-energy scaling relationships.

Abstract: Rapid charge carrier recombination is a major limiting factor over efficiency in many semiconductor photocatalysts. To address this, copper(II) oxide/titanium dioxide (CuO/TiO2) heterojunctions were synthesised through a novel, rapid solvothermal microwave procedure using a low-cost copper precursor and commercial P25 TiO2, taking as little as five minutes to synthesise well-defined CuO nanoparticles onto the host TiO2, achieving an intimate contact. The resultant composites encompass pure CuO particles of approximately 6–7 nm diameter, confirmed by means of high resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis. Photoelectrochemical water splitting was enhanced by nearly 2 times using the junction, whilst ≈1.6 times enhancement in the photocatalytic mineralisation of a model organic pollutant 2,4-dichlorophenoxyacetic acid (2,4-D) was observed. Furthermore, we studied the initial decomposition mechanism of 2,4-D by means of GC-MS analysis. The increase in catalytic activity, investigated by impedance analysis (Mott–Schottky plots) and photoluminescence spectra, is attributed to photoelectron transfer from the more negative conduction band (CB) of TiO2 to CuO, leaving the photohole on TiO2 to take part in oxidation reactions. This strategy allows for in situ charge separation which facilitates superior photocatalytic activity for both pollutant degradation and water splitting.