Heteropoly compounds as catalysts for hydrogenation of propanoic acid

Bulk Keggin heteropoly acids (HPAs) H3+n[PMo12-nVnO40] (n=0–2) and their Cs+ salts catalyse the vapour-phase hydrogenation of propanoic acid at 350?°C and 1 bar H2 pressure, yielding propanal together with 3-pentanone and propane as the main products. Catalyst acidity (controlled by Cs substitution) has crucial effect on the reaction selectivity. As the Cs content increases, the selectivity to propanal passes a maximum (74–76%). At the same time, the selectivity to propane sharply decreases, whereas 3-pentanone selectivity increases monotonously. This indicates that 3-pentanone is likely to form via Cs propanoate intermediate. Partial substitution of Mo(VI) by V(V) in the PMo12O3-40 anion has a small effect on the catalyst performance. Initially crystalline, the catalysts become amorphous after reaction, with their surface area significantly reduced. As evidenced by FTIR, H4[PMo11VO40] and its Cs salts, possessing a higher thermal stability, retain the Keggin structure in their bulk after reaction, whereas less stable H3[PMo12O40] and H5[PMo10V2O40] derivatives undergo decomposition. This shows that the as-made crystalline heteropoly compounds are catalyst precursors rather than the true catalysts. The reaction over Cs2.4H1.6[PMo11VO40] is zero order in propanoic acid with an activation energy of 85 kJ/mol. The formation of propanal is suggested to occur via a Mars–Van Krevelen mechanism

High Surface Area Conjugated Microporous Polymers: The Importance of Reaction Solvent Choice

The choice of reaction solvent has a major influence on the surface area and pore volume in conjugated microporous polymer (CMP) networks synthesized by Sonogashira-Hagihara palladium-catalyzed cross-coupling chemistry of aromatic dibromo monomers with 1,3,5-triethynylbenzene. Four solvents were evaluated for these reactions: N,N-dimethylformamide (DMF), 1,4-dioxane, tetrahydrofuran (THF), and toluene. Networks synthesized in DMF tend to exhibit the highest surface areas (up to 1260 m2/g), whereas those synthesized in toluene have on average significantly lower surface areas and pore volumes. By judicious choice of reaction solvent, microporous materials can be prepared which combine high surface area with a variety of functional groups of interest in applications such as gas storage, molecular separations, and catalysis

Branching out with aminals: microporous organic polymers from difunctional monomers

Microporous organic polymers (MOPs) have been prepared via one-pot polycondensation reactions between aldehydes and amines. Primary amines were reacted with imines to produce porous polymers from A2 + B2 monomer combinations. The resulting networks exhibit BET surface areas in the range 500–600 m2 g−1. This approach opens up the possibility of synthesising MOPs using readily-available and inexpensive precursors

Bulk superconductivity at 38K in a molecular system

C<sub>60</sub>based solids<sup>1</sup> are archetypal molecular superconductors with transition temperatures (T<sub>c</sub>) as high as 33 K (refs 2–4). T<sub>c</sub> of face-centred-cubic (f.c.c.) A<sub>3</sub>C<sub>60</sub> (A=alkali metal) increases monotonically with inter C<sub>60</sub> separation, which is controlled by the A<sup>+</sup> cation size. As Cs<sup>+</sup> is the largest such ion, Cs<sub>3</sub>C<sub>60</sub> is a key material in this family. Previous studies revealing trace superconductivity in Cs<sub>x</sub>C<sub>60</sub> materials have not identified the structure or composition of the superconducting phase owing to extremely small shielding fractions and low crystallinity. Here, we show that superconducting Cs<sub>3</sub>C<sub>60</sub> can be reproducibly isolated by solvent-controlled synthesis and has the highest T<sub>c</sub> of any molecular material at 38 K. In contrast to other A<sub>3</sub>C<sub>60</sub>materials, two distinct cubic Cs<sub>3</sub>C<sub>60</sub> structures are accessible. Although f.c.c. Cs<sub>3</sub>C<sub>60</sub> can be synthesized, the superconducting phase has the A15 structure based uniquely among fullerides on body-centred-cubic packing. Application of hydrostatic pressure controllably tunes A15 Cs<sub>3</sub>C<sub>60</sub> from insulating at ambient pressure to superconducting without crystal structure change and reveals a broad maximum in T<sub>c</sub> at []7 kbar. We attribute the observed T<sub>c</sub> maximum as a function of inter C<sub>60</sub>separation—unprecedented in fullerides but reminiscent of the atom-based cuprate superconductors—to the role of strong electronic correlations near the metal–insulator transition onset

Microporous Poly(tri(4-ethynylphenyl)amine) Networks: Synthesis, Properties, and Atomistic Simulation

Microporous poly(tri(4-ethynylphenyl)amine) networks were synthesized by palladium-catalyzed Sonogashira-Hagihara cross-coupling chemistry with apparent Brunauer-Emmet-Teller (BET) specific surface areas in the range 500-1100 m2/g. It was found that very fine synthetic control over physical properties such as BET surface area, Langmuir surface area, micropore surface area, micropore volume, and bulk density could be achieved by varying the average monomer strut length. The micropore structure and micropore surface area were rationalized by atomistic simulations for one network, NCMP-0, based on multiple physical characterization data

High Surface Area Contorted Conjugated Microporous Polymers Based on Spiro-Bipropylenedioxythiophene

Conjugated polymers derived from thiophene or 3,4-ethylenedioxythiophene derivatives have been widely investigated for use in organic thin-film transistors and organic photovoltaic devices. We describe here the synthesis of a series of conjugated microporous polymers formed by reaction of spiro-bis(2,5-dibromopropylenedioxythiophene) with one of three di- or triethynyl monomers. These polymers have surface areas up to 1631 m2/g and exhibit significant microporosity, suggesting possible applications in the fields of organic electronics or optoelectronics