MnOx-Promoted PdAg Alloy Nanoparticles for the Additive-Free Dehydrogenation of Formic Acid at Room Temperature

Formic acid (HCOOH) has a great potential as a safe and a convenient hydrogen carrier for fuel cell applications. However, efficient and CO-free hydrogen production through the decomposition of formic acid at low temperatures (<363 K) in the absence of additives constitutes a major challenge. Herein, we present a new heterogeneous catalyst system composed of bimetallic PdAg alloy and MnOx nanoparticles supported on amine-grafted silica facilitating the liberation of hydrogen at room temperature through the dehydrogenation of formic acid in the absence of any additives with remarkable activity (330 mol H2·mol catalyst-1·h-1) and selectivity (>99%) at complete conversion (>99%). Moreover this new catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching, and CO poisoning. Through a comprehensive set of structural and functional characterization experiments, mechanistic origins of the unusually high catalytic activity, selectivity, and stability of this unique catalytic system are elucidated. Current heterogeneous catalytic architecture presents itself as an excellent contender for clean hydrogen production via room-temperature additive-free dehydrogenation of formic acid for on-board hydrogen fuel cell applications. © 2015 American Chemical Society

Post-functionalized iridium Zr-MOF as a promising recycle catalyst for the hydrogenation of aromatics

[EN] The multifunctional heterogeneous catalyst iridium–Zr-based MOF is able to effectively catalyze the hydrogenation of aromatic compounds in high yields under mild conditions. The catalyst was found to be highly active and reusable, giving similar reactivity and selectivity after at least five catalytic uses.We thank the MINECO of Spain (project MAT2011-29020-C02-02), Consolider-Ingenio 2010-(CSD-0050-MULTICAT). for financial support. A.M.R.A. thanks MINECO for the FPI program.Rasero Almansa, AM.; Corma Canós, A.; Iglesias, M.; Sánchez Alonso, F. (2014). Post-functionalized iridium Zr-MOF as a promising recycle catalyst for the hydrogenation of aromatics. Green Chemistry. 16(7):3522-3527. https://doi.org/10.1039/c4gc00581cS3522352716

Dehydrocoupling of dimethylamine-borane promoted by manganese(II) m-terphenyl complexes

Two- and three-coordinate manganese m-terphenyl complexes are precatalysts for the dehydrogenation of dimethylamine-borane (Me2NH·BH3) affording one equivalent of molecular hydrogen and half an equivalent of [Me2N–BH2]2. Experimental studies into the nature of the catalyst indicate that small changes in the coordination environment give rise to significant differences in the reaction mechanism, occurring through a homogeneous mechanism for two-coordinate precatalysts, whilst for the three-coordinate species a heterogeneous mechanism takes place where nanoparticles are responsible for the catalysis

Strategic examination of the classical catalysis of formic acid decomposition for intermittent hydrogen production, storage and supply: A review

Practically, an ideal catalyst for Formic acid-decomposition is one that best suits the reaction and significantly lowers its activation energy and improves the reaction rate under favourable conditions. Several catalysts for Formic Acid (FA)-decomposition reactions were examined. Based on the volcano curve and the potential of copper to give high hydrogen yields, emphasis was placed on a Cu-catalysed reaction as potential system for sustainable hydrogen production. Some recent advances in hydrogen production from formic acid were discussed and an effective system for FA-decomposition for hydrogen production was proposed. Since helium can be stored in weather balloons and weighs almost the same as hydrogen, a hydrogen buffer made from polyester fabric and coated with polyurethane or a hydrogen cylinder/tube was proposed for storing hydrogen for use as transportfuel. Also, due to the nature of the mechanisms/pathways describing FA-conversion reactions at the sites or surfaces of the copper-nanocatalysts, it is evident that the Cu(211) coordination site possesses the highest activation energy relative to those of Cu(100) and Cu(111), hence, the reason for the noticeable high or low hydrogen yields. Thus, the potential of Cu giving high hydrogen yields from FA spans from the reactions of FA at the Cu(111) and Cu(100) sites

Heteroatom Donor‐Decorated Polymer‐Immobilized Ionic Liquid Stabilized Palladium Nanoparticles : Efficient Catalysts for Room‐Temperature Suzuki‐Miyaura Cross‐Coupling in Aqueous Media

Palladium nanoparticles stabilized by heteroatom donor‐modified polystyrene‐based polymer immobilized ionic liquids (PdNP@HAD‐PIILP; HAD‐PPh2, OMe, NH2, CN, pyrrolidone) are highly efficient catalysts for the Suzuki‐Miyaura cross‐coupling in aqueous media under mild conditions. Catalyst modified with phosphine was consistently the most efficient as it gave high yields across a range of substrates under mild conditions at low catalyst loadings. Incorporation of polyethylene glycol into the phosphine modified immobilised ionic liquid support improved catalyst efficacy by improving dispersibility and facilitating access to the active site. Moreover, each of the heteroatom modified catalysts was more active than the corresponding unsubstituted imidazolium‐based polystyrene benchmark as well as commercial samples of Pd/C. Catalyst generated in situ from either [PdCl4]@PPh2‐PIILP or its PEGylated counterpart [PdCl4]@PPh2‐PEGPIILP, by reduction with phenylboronic acid, outperformed their pre‐formed counterparts for the vast majority of substrates examined. The turnover frequency of 16,300 h−1 obtained at room temperature is one of the highest to be reported for palladium nanoparticle‐catalysed Suzuki‐Miyaura cross‐coupling between 4‐bromoacetophenone and phenylboronic acid in aqueous media under such mild conditions

Zeolite confined nanostructured dinuclear ruthenium clusters: preparation, characterization and catalytic properties in the aerobic oxidation of alcohols under mild conditions

Zeolite confined nanostructured dinuclear ruthenium clusters as a novel material were prepared by a simple three step procedure: (i) the ion-exchange of Ru3+ ions with the extra-framework Na+ ions in zeolite-Y, (ii) reduction of the Ru3+ ions within the cavities of zeolite with borohydride ions in aqueous solution all at room temperature, (iii) drying the isolated samples under aerobic conditions at 100 +/- 1.0 degrees C. The composition, morphology and structure of zeolite confined nanostructured dinuclear ruthenium clusters, as well as the integrity and crystallinity of the host material, were investigated by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, Raman, FTIR, Ru K-edge XANES, EXAFS spectroscopies, and N-2-adsorption/desorption technique. The results of these multi-pronged analyses reveal the formation of nanostructured dinuclear ruthenium clusters within the cavities of zeolite-Y, in which each ruthenium center exists in the oxidation state of 3+ and is surrounded by one oxygen of the zeolite framework and three hydroxyl ligands, without causing alteration of the framework lattice, mesopore formation, or loss of crystallinity of the host material. The catalytic use of zeolite confined nanostructured dinuclear ruthenium(III) clusters was tested in the aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl compounds and found to provide exceptional catalytic activity and selectivity under mild conditions (80 degrees C and 1 atm O-2 or air)

Hydrogen generation from hydrolysis of sodium borohydride using Ru(0) nanoclusters as catalyst

Sodium borohydride is stable in aqueous alkaline solution, however, it hydrolyses in water to hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. Generating H-2 catalytically from NaBH4 solutions has many advantages: NaBH4 solutions are nonflammable, reaction products are environmentally benign, rate of H-2 generation is easily controlled, the reaction product NaBO2 can be recycled, H-2 can be generated even at low temperatures. All of the catalysts that has been used in hydrolysis of sodium borohydride are bulk metals and they act as heterogeneous catalysts. The limited surface area of the heterogeneous catalysts causes lower catalytic activity as the activity of catalyst is directly related to its surface area. Thus, the use of metal nanoparticles with large surface area provides potential route to increase the catalytic activity. Here, we report, for the first time, the use of ruthenium(0) nanoclusters as catalyst in the hydrolysis of sodium borohydride liberating hydrogen gas. The ruthenium nanoparticles are generated from the reduction of ruthenium(III) chloride by sodium borohydride in water and stabilized by specific ligand. The ruthenium(0) nanoclusters are found to be highly active catalyst for the hydrolysis of sodium borohydride