ChemSusChem

Going uphill: The diverse chemistry established for phosphorus is mainly focused on neutral or anionic examples. Therefore, an extension of research efforts towards cationic phosphorus compounds would be desirable. However, the preparation of such compounds is restricted because of synthetic limitations. In their Full Paper on page 1805, Jan J. Weigand and co-workers at the University of Münster describe a new method for the conversion of phosphane oxides into synthetically useful cationic organophosphorus compounds using a highly-charged phosphorus-centered trication under very mild reaction and work-up conditions. Furthermore, the protocol developed for the reaction might also be applicable for the transformation of functional phosphane oxides, implementing a novel synthetic route to tertiary phosphanes that are used as ligands in transition-metal-mediated reactions.

Carbon attacks! Activated carbon and other types of carbonaceous materials have been widely used as catalysts and supports to promote the degradation of organic pollutants by the generation of hydroxyl radicals from H₂O₂.

Borane and ammonia have an issue: Ammonia borane, NH₃BH₃, is a promising hydrogen storage material owing to its high hydrogen density (19.6 wt % and 0.145 kg L⁻¹) and its ability to release H₂ through hydrolysis under ambient conditions. However, the implementation of this reaction is impeded by fundamental issues affecting all of the chemical compounds involved in the process. The discussion of these issues forms the core of this Minireview.

An electron injection highway: CdSe nanorods with CdS seed material were applied to a quantum rod-sensitized TiO₂ solar cell that showed a higher electron injection efficiency than analogous quantum dot-sensitized solar cells: reducing the nanocrystals′ carrier confinement dimensions can improve electron injection efficiency of nanocrystal-sensitized solar cells.

Solving problems: An isopropyl alcohol-mediated reaction system for the production of 5-hydroxymethylfurfural (HMF) from fructose reaches a yield of up to 87 %. The solvent can be easily recycled by evaporation, giving the HMF product. The system avoids the use of large amounts of organic solvent, has a minimal environmental impact, and offers a new route to large-scale economically viable processes.

Copper/silica nanocomposite catalysts prove efficient for the direct hydrocyclization of biomass-derived levulinic acid to cyclic 2-methyltetrahydrofuran in the vapor phase, at moderate hydrogen pressures. A nickel-promoted copper/silica catalyst with a high copper loading (72 wt %) is particularly effective for the direct hydrocyclization (89 % selectivity). The catalysts are stable during long-term experiments, showing little sign of leaching or sintering.

A nanofiber electrode is fabricated by electrospinning an ink composed of Pt/C catalyst particles in a solution of Nafion and poly(acrylic acid). Exceptionally high power densities and platinum mass activity are achieved when using the mat as cathode in H₂/air and H₂/O₂ fuel cell membrane–electrode assemblies. The nanofiber cathode also exhibits outstanding stability in accelerated durability tests.

Cool cats don′t feel pressure: Furfural is catalytically converted into octane in high yields at relatively low pressures and temperatures. In a three-step process, two bifunctional catalysts, Pt/Co₂AlO₄ and Pt/NbOPO₄, play crucial roles in achieving C₈-ols from 4-(2-furyl)-3-buten-2-one and transforming the C₈-ols into octane, respectively.

Hidden depths: Heterogeneous catalysts containing single-site ruthenium–bis-N-heterocyclic carbene (NHC) species are obtained by designing tailored hybrid organic–inorganic materials and in situ transformations, leading to final Ru-NHC units. These catalysts represent promising alternatives to homogeneous complexes with comparable activities (turnover number of ca. 3000).

N Y Pd: A zeolite-Y-confined Pd catalyst, PdCl₂(phen)@Y, enables the synthesis of glycerol carbonate by oxidative carbonylation of glycerol. Excellent conversion (95 %) and selectivity (98 %) are achieved with a very high glycerol-to-Pd molar ratio (2000). The catalyst can be re-used five times, without a significant decrease in activity and selectivity.

Robust multifunctional membranes: Reactive membranes can be synthesized on a common, highly versatile support, polyvinylidene fluoride/poly(acrylic acid) membrane pores, by immobilization of enzymes or nanoparticles. Bioreactor–nanodomain interactions and mixed matrix nanocomposite membranes provide a versatile system compared to conventional membranes that can be applied to catalysis of chemically important reactions.

Straight to the carbonate: 1,2- and 1,3-diols have been converted into the corresponding 5- and 6-membered cyclic carbonates by direct palladium-catalyzed oxidative carbonylation using only O₂ as the oxidizing agent. The method is applied to the synthesis of high-value-added glycerol carbonate from glycerol, a readily available feedstock.

Very synsible: The multistep integration of hydrogen-selective membranes into catalytic partial oxidation technology to convert natural gas into syngas and hydrogen is reported. Obtaining the same feed conversion at milder operating conditions translates into reduced natural gas consumption (and CO₂ emissions) and a reduction in variable operative costs of approximately 10 % compared to conventional catalytic partial oxidation.

Morphological control by ionic liquids: The physical and chemical properties of ZnO nanomaterials is critically dependent on particle size, (surface) defects, and morphology, which makes the development of synthesis protocols, which are optimized for well-defined ZnO nanostructures, essential. We report a fast and efficient, yet morphologically selective, synthetic route in ionic liquids.

Going uphill: A protocol for the smooth conversion of the resistant PO bond in phosphane oxides into a reactive PN bond of synthetically useful pyrazolylphosphonium salts by a highly-charged, oxophilic phosphorus-centered trication is described. The reactions are conducted at room temperature with quantitative yields. We aim towards alternatives to existing reduction methods for phosphane oxide functionalization.

Manganese starts acting cagey: 3D cage-like, phenyl group-modified, periodic mesoporous organosilica-entrapped, dimeric manganese–salen complexes prepared by entrapment and silylation exhibit considerably higher catalytic activity and stability towards the epoxidation of alkenes than their monomeric analogues and the starting homogeneous dimeric manganese–salen complexes.

Turning up the stereo: An efficient three-step strategy for synthesizing chiral biobased dideoxy-diamino isoidide and dideoxy-diamino isosorbide in high yield with absolute stereo control is described. These highly interesting chiral building blocks are presently the subject of several investigations due to their application in high-performance biobased polymers such as polyamides and polyurethanes.

An epoxcellent discovery: Multilayered, covalently supported ionic liquid phase (mlc-SILP) materials are successfully prepared and used as catalysts for the cycloaddition of carbon dioxide to epoxides, yielding cyclic carbonates. The materials are highly active, show improved productivity compared to known supported ionic liquid catalysts, and can be easily recovered and reused without loss of activity.

Reactive extraction: A hydrophobic mixture of butyl levulinate (BL) and formate (BF) esters, formed by the reactive extraction of cellulose-derived levulinic acid and formic acid, separates spontaneously from aqueous H₂SO₄ solution, which is recovered and recycled. BL is reduced to γ-valerolactone over a supported gold catalyst using BF as the sole source of hydrogen.

Ca and Al together forever: Ca-rich Ca–Al–O oxides, with Ca²⁺/Al³⁺ ratios of 1:1, 3:1, 5:1, and 7:1, are prepared by using hydrothermal decomposition of coprecipitated hydrotalcite-like Ca–Al–CO₃ precursors. We demonstrate that these Ca–Al–O sorbents are suitable for long-term cyclic operation for high-temperature CO₂ adsorption at 500–700 °C.