Electronic band structures in hydrogenated graphene are theoretically investigated by means of first-principle calculations and an effective tight-binding model. It is shown that regularly designed ...hydrogenation to graphene gives rise to a large band gap about 1 eV. Remarkably, by changing the spatial pattern of the hydrogenation, topologically distinct states can be realized, where the topological nontriviality is detected by C2 parity indices in bulk and confirmed by the existence of gapless edge/interface states as protected by the mirror and sublattice symmetries. The analysis of the wave functions reveals that the helical edge states in hydrogenated graphene with the appropriate design carry pseudospin currents that are reminiscent of the quantum spin Hall effect. Our work shows the potential of hydrogenated graphene in pseudospin-based device applications.
Ni/CaO, a low-cost dual-functional material (DFM), has been widely studied for integrated COsub.2 capture and hydrogenation. The core of this dual-functional material should possess both good COsub.2 ...capture–conversion performance and structural stability. Here, we synthesized Ni/CaO DFMs modified with alkali metals (Na, K, and Li) through a combination of precipitation and combustion methods. It was found that Na-modified Ni/CaO (Na-Ni/CaO) DFM offered stable COsub.2 capture–conversion activity over 20 cycles, with a high COsub.2 capture capacity of 10.8 mmol/g and a high COsub.2 conversion rate of 60.5% at the same temperature of 650 °C. The enhanced COsub.2 capture capacity was attributed to the improved surface basicity of Na-Ni/CaO. In addition, the incorporation of Na into DFMs had a favorable effect on the formation of double salts, which shorten the COsub.2 capture and release process and promoted DFM stability by hindering their aggregation and the sintering of DFMs.
The Au/Ni/Ni(OH).sub.2/C bimetallic nanocatalysts with different Au loadings (Au/Ni/Ni(OH).sub.2/C-1: 0.05 wt%Au; Au/Ni/Ni(OH).sub.2/C-2: 0.46 wt%Au; Au/Ni/Ni(OH).sub.2/C-3: 2.60 wt%Au) were prepared ...at room temperature. The characterization results proved the nanostructure of Au islands supported on the Ni/Ni(OH).sub.2 nanoparticles (NPs) and synergy effect of Au-, Ni- and Ni(OH).sub.2-related species in Au/Ni/Ni(OH).sub.2/C. These are the main reasons why their catalytic performance and selectivity to m-nitroaniline in m-dinitrobenzene hydrogenation were much higher than those of monometallic catalysts (Au/C and Ni/Ni(OH).sub.2/C). Because Au/Ni/Ni(OH).sub.2/C-2 was with high dispersion of Au, Au(0)/Au.sup.n+ ratioalmost equal to1:1 on the surface, novel nanostructure, moderate capacity of activating and dissociating hydrogen, and synergistic effect, it had much better catalytic activity (conversion of m-dinitrobenzene-100%) and higher selectivity to m-nitroaniline (95.0%) in m-dinitrobenzene hydrogenation reaction compared to other two supported bimetallic catalysts (Au/Ni/Ni(OH).sub.2/C-1 and Au/Ni/Ni(OH).sub.2/C-3). Au/Ni/Ni(OH).sub.2/C-2 also exhibited high stability. Graphic abstract
Several phosphonium and ammonium triarylborohydrides, which are intermediates in hydrogenation reactions catalyzed by frustrated Lewis pairs, were synthesized in high yield under mild conditions from ...triaryl boranes, ammonium or phosphonium halides, and triethylsilane. The kinetics and mechanisms of the reactions of these hydridoborate salts with benzhydrylium ions, iminium ions, quinone methides, and Michael acceptors were investigated, and their nucleophilicity was determined and compared with that of other hydride donors.
The hydrogenation of oximes and oxime ethers is usually hampered by NO bond cleavage, hence affording amines rather than hydroxylamines. The boron Lewis acid B(C6F5)3 is found to catalyze the ...chemoselective hydrogenation of oxime ethers at elevated or even room temperature under 100bar dihydrogen pressure. The use of the triisopropylsilyl group as a protecting group allows for facile liberation of the free hydroxylamines.
The front cover artwork for Issue 14/2016 is provided by Dr. Gawande and Prof. Zboril, from the Regional Centre of Advanced Technologies and Materials, Palacky University, Olomouc (Czech Republic). ...The image shows an efficient protocol for the transfer hydrogenation of nitroarenes using flower‐shaped micro‐mesoporous iron oxide nanocatalysts with formic acid as the reducing agent to obtain good to excellent yields of the respective amines. See the Full Paper itself at http://dx.doi.org/10.1002/cctc.201600296.
“This catalyst is accessible from inexpensive metal‐based materials” This and more about the story behind the research featured on the front cover can be found in this issue's Cover Profile. Read the full text of the corresponding research at http://dx.doi.org/10.1002/cctc.201600296.
DRIFTS experiments such as CO adsorption, CO-TPSR and CO+H.sub.2 were designated to study the effect of Fe promoter on the key steps of C.sub.2 oxygenates formation from syngas. The CO adsorption ...results demonstrated that Fe weakened CO adsorption and especially the bridging adsorption. It was found in CO-TPSR experiments that the catalyst with lower Fe loading is more easily dissociated while the ones with higher Fe loading own stronger hydrogenation activity. Moreover, it was observed by CO+H.sub.2 experiments that Fe plays a role in stabilizing the lineally adsorbed CO species and decreasing the CO desorption rate. The catalytic performance results indicated that when Fe content is 4wt. %, the selectivity of total C.sub.2 oxygenates is the highest, which was in accordance with the DRIFTS results.
The mechanism of Y on H/H2 adsorption performance of Mg17Al12 were studied by the density functional theory. We obtained that for the Y-adsorbed systems, Y tended to occupy on the bridge site between ...adjacent Mg atoms. For the Y-substituted surfaces, Y atoms inclined to replace Mg atoms on the surfaces. We found that hydrogen (H/H2) absorption on the Mg17Al12(110) systems were improved by adding Y, the order of adsorption energy was as follows: clean Mg17Al12(110) > the Y-substituted surfaces > the Y-adsorbed surfaces. In addition, H2 molecules could dissociate on the Y-containing systems without barrier energy. Electronic properties showed that for H2 adsorption, the s states of atomic H mainly hybridized with the d states of Y. The formations of the Y-H bonds and the interactions between Y and H atoms could expound the mechanism for the promoted hydrogenation performance of the Y-containing surfaces.
Hydrogenation of biomass-derived furfuryl alcohol to widely used tetrahydrofurfuryl alcohol is an important industrial route, which however calls for a more efficient catalyst. In this work, a highly ...selective and stable Ni-C-Al.sub.2O.sub.3 catalyst for furfuryl alcohol hydrogenation to tetrahydrofurfuryl alcohol is reported. The catalyst precursor is prepared by in-situ growth of Ni-based metal organic frameworks (Ni-BTC) on Al.sub.2O.sub.3 and then the precursor undergoes thermal decomposition to obtain the catalyst directly. For comparison, Ni-C/Al.sub.2O.sub.3 acquired from pyrolysis of physically mixed Ni-MOFs with Al.sub.2O.sub.3 and Ni/Al.sub.2O.sub.3 prepared by impregnation method are also tested as the hydrogenation catalysts. The prepared catalysts are characterized by a series of techniques, including XRD, FT-IR, TG, TEM, SEM, XPS and BET to reveal the relationship between the catalysts structure and their performance. The results show that small metal Ni particle size and appropriate interaction between Ni and the support, which benefit from the in-situ preparation method are key factors that ensure the high furfuryl alcohol conversion (99.8%) and high selectivity to tetrahydrofurfuryl alcohol (98.2%) at moderate reaction conditions (120 °C, 30 min, 4 MPa H.sub.2).
Sulfur-protected enantiopure P-chiral 1-phosphanorbornane silyl ethers 5a,b are obtained in high yields via the reaction of the hydroxy group of P-chiral 1-phosphanorbornane alcohol 4 with ...tert-butyldimethylsilyl chloride (TBDMSCl) and triphenylsilyl chloride (TPSCl). The corresponding optically pure silyl ethers 5a,b are purified via crystallization and fully structurally characterized. Desulfurization with excess Raney nickel gives access to bulky monodentate enantiopure phosphorus(III) 1-phosphanorbornane silyl ethers 6a,b which are subsequently applied as ligands in iridium-catalyzed asymmetric hydrogenation of a prochiral ketone and enamide. Better activity and selectivity were observed in the latter case.
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