ChemCatChem

The cover picture shows the olefin hydrogenation reaction inside the porous structure of AEPF-1, a calcium-based metal–organic framework (MOF). In their Communication on page 147 ff., Gutiérrez-Puebla et al. describe the preparation and studies of this material, which is a highly efficient heterogeneous catalyst for the hydrogenation of styrene to form ethylbenzene under mild conditions. The calcium-based MOF is a comparatively cheap and green alternative to conventional precious metal-based alkene hydrogenation catalysts.

Vive la différence! Spatially isolated, multifunctional Ti^IV active sites, like those in the catalyst TAPO-5 (pictured) facilitate the conversion of cyclohexene to adipic acid with H₂O₂ through a cascade of six consecutive reactions, illustrating how such solids unite the advantages of heterogeneous and homogeneous catalysts. Comparisons and contrasts between these two types of catalysts are also drawn.

Counter revolution: Most homogeneous gold-catalyzed transformations employ gold(I) complexes with weakly coordinating anions, which, their remarkable activity notwithstanding, lack stability at higher temperatures. Shi et al. have described the synthesis of simple phosphine-based gold(I) complexes with triazolates as counter ions. The compounds are highly thermostable and good catalysts for intermolecular hydroaminations.

Guten Tag: Entrapment of a catalyst in a solvent such as water or an ionic liquid can be achieved by installing an ionic substituent on the catalyst structure. Rational installation of an ionic tag onto a known catalytically active species may provide two benefits: an enhanced catalytic activity, owing to a transition-state-stabilizing electrosteric effect, and the chance to apply homogeneous biphasic conditions.

Cheap thrills: A new metal–organic framework, based on cheap, abundant calcium, with the bent ligand, 4,4′-hexafluoroisopropylidenebisbenzoic acid, serves as a highly efficient heterogeneous catalyst for the hydrogenation of styrene to form ethyl benzene under mild conditions. Complete hydrogenation occurs after 2 h at 373 K without formation of byproducts.

Highly efficient continuous-flow asymmetric catalysis was achieved by combination of supported ionic liquid phase (SILP) catalysts with supercritical CO₂ (scCO₂) as the mobile phase, as demonstrated for enantioselective hydrogenation in the presence of a molecular rhodium–QUINAPHOS complex. The integrated reaction and separation process yielded chemically and enantiomerically pure products without the need for organic solvents.

Natural selection: The copper-catalyzed diastereo- and enantioselective sequential reactions of propargylic acetates with (E)-2,4-pentadienylamine give the corresponding 1,2-disubstituted tetrahydroisoindoles in high yields with high diastereo- and enantioselectivities, in which only a single copper works as a catalyst to promote both steps: the propargylic amination and intramolecular [4+2] cycloaddition.

An electrocatalyst formed by the reduction of Pt²⁺ ions on the surface of hexagonally close-packed (hcp) Ru core nanoparticles has been prepared by a redox–transmetalation process. As a result of the significant changes in the hcp stacking order and in the d-band vacancies, Pt-on-Ru catalyst nanoparticles exhibit improved catalytic activity for the electrooxidation of methanol compared to the commercial PtRu catalyst.

That's Mo like it! The molybdenum nitride/HZSM-5 catalyst with highly dispersed MoN_x (dispersion >90 %) is very active in ammonia synthesis. The MoN_x species are more stable than bulk Mo₂N against oxidation and the catalyst demonstrates a higher catalytic performance than bulk Mo₂N.

Turning oranges to plastics! A highly selective one-step transformation of (+)-limonene (a renewable source derived from orange pulp) to the polymer building block dimethylstyrene (DMS) using a simple catalytic system has been developed. The presence of the sterically hindered base 2,6-di-tert-butylpyridine efficiently prevents migration of the exocyclic double bond during aromatization, which suppresses unwanted p-cymene formation.

Activated carbon substrates, such as glassy carbon, graphite cloth, graphite felt, and carbon fiber paper, modified to generate high concentrations of oxygenated functional groups, are used as substrates for the electrodeposition of Pt and Ru by a double potentiostatic pulse program. The resultant systems are analyzed as electrodes for methanol oxidation in acid solution. Those prepared with oxidized graphite felt exhibited the greatest activity.

Surface-enhanced selectivity: Highly selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, catalyzed by Pt and Ir supported on multiwalled carbon nanotubes, is achieved after a high temperature thermal treatment of the catalyst. Surface chemistry of the support, rather than the metal particle size, is the key factor.

Colloidal, ligand-capped Pt nanoparticles deposited on oxide supports are investigated for CO adsorption and oxidation. IR spectroscopic experiments reveal that small molecules can pass through the ligand shell and adsorb on the particle surface. The ability to penetrate the shell is dependent on the type of ligand used, which renders ligand-capped nanoparticles potentially interesting for reaction and selectivity control.

HMS Endeavour: Copper species supported on hexagonal mesoporous silica (Cu/HMS), prepared by ion exchange, exhibits high catalytic activity for the hydrogenation of dimethyl oxalate with high selectivity towards ethylene glycol. The ion-exchange temperature has profound effects on the structure of the Cu/HMS catalysts as well as on their activity and selectivity.

Grand prisms: Zinc stearate-stabilized copper nanoparticles, synthesized by an efficient one-step process, are applied in the continuous liquid-phase synthesis of methanol. The active state is identified as triangular ZnO prisms with truncated edges attached to the spherical Cu particles, which act as a reservoir for ZnO_x species diffusing onto the Cu particles and promoting the catalytic activity.