Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

Selective catalytic hydrogenation has wide applications in both petrochemical and fine chemical industries, however, it remains challenging when two or multiple functional groups coexist in the substrate. To tackle this challenge, the "active site isolation" strategy has been proved effective, and various approaches to the site isolation have been developed. In this review, we have summarized these approaches, including adsorption/grafting of N/S-containing organic molecules on the metal surface, partial covering of active metal surface by metal oxides either via doping or through strong metal-support interaction, confinement of active metal nanoparticles in micro- or mesopores of the supports, formation of bimetallic alloys or intermetallics or core@shell structures with a relatively inert metal (IB and IIB) or nonmetal element (B, C, S, etc.), and construction of single-atom catalysts on reducible oxides or inert metals. Both advantages and disadvantages of each approach toward the site isolation have been discussed for three types of chemoselective hydrogenation reactions, including alkynes/dienes to monoenes, α,β-unsaturated aldehydes/ketones to the unsaturated alcohols, and substituted nitroarenes to the corresponding anilines. The key factors affecting the catalytic activity/selectivity, in particular, the geometric and electronic structure of the active sites, are discussed with the aim to extract fundamental principles for the development of efficient and selective catalysts in hydrogenation as well as other transformations.

Selective Hydrogenation over Supported Metal Catalysts: From Nanoparticles to Single Atoms

In this contribution, we provide a comprehensive overview of C-H activation methods promoted by NHC-transition metal complexes, covering the literature since 2002 (the year of the first report on metal-NHC-catalyzed C-H activation) through June 2019, focusing on both NHC ligands and C-H activation methods. This review covers C-H activation reactions catalyzed by group 8 to 11 NHC-metal complexes. Through discussing the role of NHC ligands in promoting challenging C-H activation methods, the reader is provided with an overview of this important area and its crucial role in forging carbon-carbon and carbon-heteroatom bonds by directly engaging ubiquitous C-H bonds.

N-Heterocyclic Carbene Complexes in C–H Activation Reactions

Production of lactic acid/lactates from biomass and their catalytic transformations to commodities.

A wide variety of metal borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal borohydride derivatives have also been discovered: anion-substituted compounds where the complex borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.

Metal borohydrides and derivatives – synthesis, structure and properties

Release of ca. 17.8 wt% of hydrogen was observed from the Co-catalyzed lithium borohydride ammoniate, Li(NH3)4/3BH4 (with equivalent protic and hydridic hydrogen atoms, composed of solid Li(NH3)BH4 and liquid Li(NH3)2BH4), in the temperature range of 135 to 250 °C in a closed vessel. The low NH3 equilibrium vapor pressure of the ammoniate in the vessel results in the retention of the majority of NH3 in the vicinity of LiBH4, and thus, creates an environment favorable for the direct dehydrogenation rather than deammoniation. The dehydrogenation is a two-step process forming the intermediates Li4BN3H10 and LiBH4. The final solid residue is a mixture of BN and Li3BN2. The presence of nanosized Co catalyst effectively promote the hydrogen release.

Releasing 17.8 wt% H2 from lithium borohydride ammoniate

Converting CO2 and H2 O into carbon-based fuel by IR light is a tough task. Herein, compared with other single-component photocatalysts, the most efficient IR-light-driven CO2 reduction is achieved by an element-doped ultrathin metallic photocatalyst-Ni-doped CoS2 nanosheets (Ni-CoS2 ). The evolution rate of CH4 over Ni-CoS2 is up to 101.8 μmol g-1  h-1 . The metallic and ultrathin nature endow Ni-CoS2 with excellent IR light absorption ability. The PL spectra and Arrhenius plots indicate that Ni atoms could facilitate the separation of photogenerated carriers and the decrease of the activation energy. Moreover, in situ FTIR, DFT calculations, and CH4 -TPD reveal that the doped Ni atoms in CoS2 could effectively depress the formation energy of the *COOH, *CHO and desorption energy of CH4 . This work manifests that element doping in atomic level is a powerful way to control the reaction intermediates, providing possibilities to realize high-efficiency IR-light-driven CO2 reduction.

Efficient Infrared-Light-Driven CO2 Reduction Over Ultrathin Metallic Ni-doped CoS2 Nanosheets.

One-pot synthesis of 2-substituted benzo[b]furans via Pd–tetraphosphine catalyzed coupling of 2-halophenols with alkynes

A new ruthenium catalyst supported on glucose-derived carbon spheres was prepared by using the impregnation method and then characterized by X-ray photoelectron spectroscopy, XRD, TEM, SEM, FTIR, and solid-state 13C MAS NMR techniques. With water as the environmentally friendly solvent, the conversion of quinoline and the selectivity toward decahydroquinoline could reach 98.2 and 95.2 %, respectively, under mild conditions (reaction temperature=393 K and H2 pressure=2.0 MPa). The catalyst could be recycled thrice without decrease in activity and selectivity. The excellent catalytic performance of this catalyst may be attributed to the hydrogen bond between the hydroxyl group of the support surface and the nitrogen atom in quinoline as well as to the π–π interaction between the organic support and quinoline.

Xueli Zheng

Papers

Releasing 17.8 wt% H2 from lithium borohydride ammoniate

Efficient Infrared-Light-Driven CO2 Reduction Over Ultrathin Metallic Ni-doped CoS2 Nanosheets.

One-pot synthesis of 2-substituted benzo[b]furans via Pd–tetraphosphine catalyzed coupling of 2-halophenols with alkynes

Aqueous Phase Hydrogenation of Quinoline to Decahydroquinoline Catalyzed by Ruthenium Nanoparticles Supported on Glucose‐Derived Carbon Spheres

Effect of rare earth (RE) elements on V-based hydrogen storage alloys