Challenging thermodynamics: hydrogenation of benzene to 1,3- cyclohexadiene by Ru@Pt nanoparticles

Since the earliest reports on catalytic benzene hydrogenation, 1,3-cyclohexadiene and cyclohexene have been proposed as key intermediates. However, the former has never been obtained with remarkable selectivity. Herein we report the first partial hydrogenation of benzene towards 1,3 cyclohexadiene under mild conditions in a catalytic biphasic system consisting of Ru@Pt nanoparticles (NPs) in ionic liquid (IL). The tandem reduction of [Ru(COD)(2-methylallyl)2] (COD = 1,5 cyclooctadiene) followed by decomposition of [Pt2(dba)3] (dba = dibenzylideneacetone) in 1-nbutyl- 3 methylimidazolium hexafluorophosphate (BMI.PF6) IL under hydrogen affords core-shell Ru@Pt NPs of 2.9 ± 0.2 nm. The hydrogenation of benzene (60 ºC, 6 bar of H2) dissolved in nheptane by these bimetallic NPs in BMI.PF6 affords 1,3- cyclohexadiene in unprecedented 21% selectivity at 5% benzene conversion. On opposition, almost no 1,3-cyclohexadiene was observed using monometallic Pt(0) or Ru(0) NPs under the same reaction conditions and benzene conversions. The study reveals that the selectivity is related to synergetic effects of the bimetallic composition of the catalyst material as well as the performance under biphasic reaction conditions. It is proposed that colloidal metal catalysts in ILs and under multiphase conditions (“dynamic asymmetric mixture”) can operate far from the thermodynamic equilibrium akin to chemically active membranes

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

Molecular Chemistry to the Fore: New Insights into the Fascinating World of Photoactive Colloidal Semiconductor Nanocrystals

Colloidal semiconductor nanocrystals possess unique properties that are unmatched by other chromophores such as organic dyes or transition-metal complexes. These versatile building blocks have generated much scientific interest and found applications in bioimaging, tracking, lighting, lasing, photovoltaics, photocatalysis, thermoelectrics, and spintronics. Despite these advances, important challenges remain, notably how to produce semiconductor nanostructures with predetermined architecture, how to produce metastable semiconductor nanostructures that are hard to isolate by conventional syntheses, and how to control the degree of surface loading or valence per nanocrystal. Molecular chemists are very familiar with these issues and can use their expertise to help solve these challenges. In this Perspective, we present our group\u27s recent work on bottom-up molecular control of nanoscale composition and morphology, low-temperature photochemical routes to semiconductor heterostructures and metastable phases, solar-to-chemical energy conversion with semiconductor-based photocatalysts, and controlled surface modification of colloidal semiconductors that bypasses ligand exchange

Study of structure and electronic effect aspects of nanocatalyst for formic acid electro-oxidation

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Formate as a surface probe for ruthenium nanoparticles in solution 13C NMR spectroscopy

Formic acid adsorption on ruthemium nanoparticles of different sizes allows differentiation of differently bound formate species by solution 13C NMR spectroscopy (see picture). The chemical shifts are comparable to those of organometallic analogues, thus indicating that formate can act as a probe to distinguish surface features of metallic nanoparticles in solution with good quantification and resolution. © 2009 Wiley-VCH Verleg GmbH and Co. KgaA