Comparing the Basic Phenomena Involved in Three Methods of Pore‐size Characterization: Gas Adsorption,Liquid Intrusion and Thermoporometry

Gas adsorption at 77 K is probably the most widely used method to characterize mesoporous adsorbents via capillary condensation. Mercury intrusion is also commonly used for the characterization of such materials with the possibility to extend the pore width distribution measurement to the macropore range. More recently water intrusion was proposed to study hydrophobic porous solids. Thermoporometry is a further characterization method, now based on the study of the solid/liquid transition. We can consider that all these methods rely on the modification of the phase diagram of a pure substance under the effect of confinement. For each of them, the equations and models derived are based either on classical thermodynamics or on statistical approaches. In most cases, the derivation of the pore width distribution is carried out with the assumption that the porous system is made up of non‐connected cylinders, whereas the actual complexity of the structure is derived from the hysteresis shape. Our aim here is to compare the four approaches above (gas adsorption, mercury intrusion, water intrusion, thermoporometry) on samples giving rise, in their gas adsorption isotherms, to the typical hysteresis loops of the IUPAC classification. Our comparison is in great part carried out after the shape of the hysteresis loops obtained with the various methods and after the information it brings on the mechanism of replacement of a phase by the other within the porous system.     

Determination of cyclophosphamide and ifosfamide in sewage effluent by stable isotope-dilution liquid chromatography-tandem mass spectrometry

A reliable and specific method was developed for the determination of the cytotoxic drugs cyclophosphamide and ifosfamide in sewage effluent. The most successful combination was found to be Strata-X solid-phase extraction followed by Florisil^® clean-up with analysis by liquid chromatography–tandem mass spectrometry. Quantification by internal standardisation was achieved using custom synthesised d4-cyclophophosphamide. The mass spectrometer was operated in highly selective reaction monitoring (HSRM) mode, which significantly reduced matrix noise and improved sensitivity. Although it suffered from some ionisation suppression, electrospray ionisation (ESI) was found to give an order of magnitude better sensitivity in terms of limit of detection than atmospheric pressure chemical ionisation (APCI). Using final effluent from two different sewage treatment plants, the method was validated following official European guidelines and shown to be a high performance tool for routine analysis at the sub-nanogram per litre level. Depending on the matrix, the limit of detection for cyclophosphamide was between 0.03 ng/L and 0.12 ng/L and for ifosfamide between 0.05 ng/L and 0.09 ng/L. For cyclophosphamide the accuracy and precision, tested at 1.7 ng/L, were 98–109% and ≤13%, CV respectively. For ifosfamide the accuracy and precision, tested at 1.1 ng/L, were 98–113% and ≤15% CV, respectively. Depending on the sample matrix the absolute recovery of the internal standard was between 57% and 70%. The method was tested by analysis of spot samples taken from the final effluent discharges of two sewage treatment plants; the first using a conventional trickling filter treatment process and second employing activated sludge followed by ultra violet treatment. Cyclophosphamide was detected at 0.19 ng/L at the first plant and at the second detected at 3.7 ng/L and 3.5 ng/L, before and after the UV treatment process; ifosfamide was not detectable at either plant.     

Efficient Cluster‐Based Catalysts for Asymmetric Hydrogenation of α‐Unsaturated Carboxylic Acids

The new clusters [H₄Ru₄(CO)₁₀(μ‐1,2‐P‐P)], [H₄Ru₄(CO)₁₀(1,1‐P‐P)] and [H₄Ru₄(CO)₁₁(P‐P)] (P‐P=chiral diphosphine of the ferrocene‐based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H₄Ru₄(CO)₁₀(μ‐1,2‐P‐P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal–metal bond of the ruthenium tetrahedron in the “conventional” manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H₄Ru₄(CO)₁₀(1,1‐Walphos)] clusters isomerise to the corresponding [H₄Ru₄(CO)₁₀(μ‐1,2‐Walphos)] clusters, whereas the Josiphos‐containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α‐unsaturated carboxylic acids and the prochiral methyl ester (E)‐methyl 2‐methylbut‐2‐enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos‐containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99–100 %), product selectivities (99–100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos‐containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high‐pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H₄Ru₄(CO)₁₀(μ‐1,2‐P‐P)] clusters (P‐P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P‐P)(carboxylato)₂] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species.     

Efficient Cluster-Based Catalysts for Asymmetric Hydrogenation of α-Unsaturated Carboxylic Acids

The new clusters [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)], [H(4) Ru(4) (CO)(10) (1,1-P-P)] and [H(4) Ru(4) (CO)(11) (P-P)] (P-P=chiral diphosphine of the ferrocene-based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal-metal bond of the ruthenium tetrahedron in the "conventional" manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H(4) Ru(4) (CO)(10) (1,1-Walphos)] clusters isomerise to the corresponding [H(4) Ru(4) (CO)(10) (μ-1,2-Walphos)] clusters, whereas the Josiphos-containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α-unsaturated carboxylic acids and the prochiral methyl ester (E)-methyl 2-methylbut-2-enoate. High conversion rates (>94?%) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos-containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99-100?%), product selectivities (99-100?% in most cases) and good enantioselectivities, reaching 90?% enantiomeric excess (ee) in certain cases, were observed for the Walphos-containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high-pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H(4) Ru(4) (CO)(10) (μ-1,2-P-P)] clusters (P-P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P-P)(carboxylato)(2) ] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species.     

Acetylene and argon adsorption in a supramolecular organic zeolite

The adsorption properties of a new nanoporous organic zeolite with respect to acetylene and Ar were studied by volumetric adsorption analysis, microcalorimetric experiments, and synchrotron high-resolution X-ray powder diffraction. This allowed us to locate the guest molecules inside the host channels and characterize the host-guest interactions.     

Separation of CO2-CH4 mixtures in the mesoporous MIL-100(Cr) MOF: experimental and modelling approaches

Carbon dioxide is the main undesirable compound present in raw natural gas and biogas. Physisorption based adsorption processes such as pressure swing adsorption (PSA) are one of the solutions to selectively adsorb CO(2) from CH(4). Some hybrid crystalline porous materials that belong to the family of metal-organic frameworks (MOFs) show larger CO(2) adsorption capacity compared to the usual industrial adsorbents, such as zeolites and most activated carbons, which makes them potentially promising for such applications. However, their selectivity values have been most often determined using only single gas adsorption measurements combined with simple macroscopic thermodynamic models or by means of molecular simulations based on generic forcefields. The transfer of this systematic approach to all MOFs, whatever their complex physico-chemical features, needs to be considered with caution. In contrast, direct co-adsorption measurements collected on these new materials are still scarce. The aim of this study is to perform a complete analysis of the CO(2)-CH(4) co-adsorption in the mesoporous MIL-100(Cr) MOF (MIL stands for Materials from Institut Lavoisier) by means of a synergic combination of outstanding experimental and modelling tools. This solid has been chosen both for its fundamental interests, given its very large CO(2) adsorption capacities and its complexity with a combination of micropores and mesopores and the existence of unsaturated accessible metal sites. The predictions obtained by means of Grand Canonical Monte Carlo simulations based on generic forcefields as well as macroscopic thermodynamic (IAST, RAST) models will be compared to direct the co-adsorption experimental data (breakthrough curve and volumetric measurements).     

How water fosters a remarkable 5-fold increase in low-pressure CO2 uptake within mesoporous MIL-100(Fe)

The uptake and adsorption enthalpy of carbon dioxide at 0.2 bar have been studied in three different topical porous MOF samples, HKUST-1, UiO-66(Zr), and MIL-100(Fe), after having been pre-equilibrated under different relative humidities (3, 10, 20, 40%) of water vapor. If in the case of microporous UiO-66, CO(2) uptake remained similar whatever the relative humidity, and correlations were difficult for microporous HKUST-1 due to its relative instability toward water vapor. In the case of MIL-100(Fe), a remarkable 5-fold increase in CO(2) uptake was observed with increasing RH, up to 105 mg g(-1) CO(2) at 40% RH, in parallel with a large decrease in enthalpy measured. Cycling measurements show slight differences for the initial three cycles and complete reversibility with further cycles. These results suggest an enhanced solubility of CO(2) in the water-filled mesopores of MIL-100(Fe).     

The chromatographic analysis of organic peroxides

Organic peroxides can be identified by reversed-phase chromatography on siliconc-treated paper, a chloroform-ethanol-water mixture is used as solvent, and the spray reagent is acidified ferrous thiocyanate.Peroxides of low molecular weight are lost from the paper by volatilisation, these can be identified and estimated by vapour-phase chromatography.     

Isospin bounds for energy partition in ee and NN annihilation

In reactions such as $\text{e}$e → anything, $\text{N}$N → anything, the final state (neglecting secondary isospin violating decays) is customarily supposed to have isospin zero or one. We show that for such states the average fraction (X) of the energy carried away by neutral pions is bounded by $\text{X<}\text{(9+√41)}\text{20}\text{≈0.77}$, when I₃ = 0 (e.g., for ee, pp, nn) and by $\text{X>}\text{(11?√41)}\text{40}\text{≈0.115}$, when I₃=±1 (e.g., for pn or np).