Hydrogen Sulfide Adsorption on MOFs and MOF/Graphite Oxide Composites

Composites of a copper‐based metal‐organic framework (MOF) and graphite oxide (GO) were tested for hydrogen sulfide removal at ambient conditions. In order to understand the mechanisms of adsorption, the initial and exhausted samples were analyzed by various techniques including X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, and sorption of nitrogen. Compared to the parent materials, an enhancement in hydrogen sulfide adsorption was found. It was the result of physical adsorption of water and H₂S in the pore space formed at the interface between the MOF units and the graphene layers where the dispersive forces are the strongest. Besides physisorption, reactive adsorption was found as the main mechanism of retention. H₂S molecules bind to the copper centers of the MOF. They progressively react with the MOF units resulting in the formation of copper sulfide. This leads to the collapse of the MOF structure. Water enhances adsorption in the composites as it allows the dissolution of hydrogen sulfide.     

A Strategy Utilizing a Recyclable Macrocycle Transporter for the Efficient Synthesis of a Triazolium‐Based [2]Rotaxane

A general synthesis of triazolium‐containing [2]rotaxanes, which could not be accessed by other methods, is reported. It is based on a sequential strategy starting from a well‐designed macrocycle transporter which contains a template for dibenzo‐24‐crown‐8 and a N‐hydroxysuccinimide (NHS) moiety. The sequence is: 1) synthesis by slippage of a [2]rotaxane building‐block; 2) its elongation at its NHS end; 3) the delivery of the macrocycle to the elongated part of the axle by an induced translational motion; 4) the contraction process to yield the targeted [2]rotaxane and recycle the initial transporter.     

Facile Synthesis of 1,2-bis-(Cyanomethyl)Benzenes

3-Alkoxy-1,2-bis-(cyanomethyl)benzenes can be prepared in two steps, in high yield, from m-alkoxy-N.N-dimethylbenzylamines by directed metallation followed by ethyl chloroformate-promoted cyanide displacement.     

Synthesis of fluorinated pseudopeptides: metal mediated reversal of stereochemistry in diastereoselective addition of organometallic reagents to N-(tert-butanesulfinyl)-α-fluoroenimines

The addition reaction of organometallic reagents to N-(tert-butanesulfinyl)-α-fluoroenimines was studied. Depending of the nature of the organometallic species (Grignard reagents or zincate complexes), we were able to control the configuration of the newly created stereogenic centers in high yields with good to high diastereomeric ratios. The chiral β-fluoro allylamines are key synthons toward the synthesis of fluorinated pseudopeptides bearing a fluoroolefin moiety as a peptide bond mimic.     

On stabilization and control for the critical Klein-Gordon equation on a 3-D compact manifold

In this article, we study the internal stabilization and control of the critical nonlinear Klein-Gordon equation on 3-D compact manifolds. Under a geometric assumption slightly stronger than the classical geometric control condition, we prove exponential decay for some solutions bounded in the energy space but small in a lower norm. The proof combines profile decomposition and microlocal arguments. This profile decomposition, analogous to the one of Bahouri and Gérard (1999) [2] on R³, is performed by taking care of possible geometric effects. It uses some results of S. Ibrahim (2004) [21] on the behavior of concentrating waves on manifolds.     

Catalytic C-H amination: the stereoselectivity issue

Catalytic C-H amination has recently emerged as a unique tool for the synthesis of amines. This tutorial review highlights the existing protocols catalyzed by metal complexes (rhodium, copper, ruthenium, manganese and palladium) allowing diastereo- and enantioselective C-H amination. Substrate-, catalyst- and reagent-controlled methodologies are detailed. They involve either catalytic nitrene C-H insertion or C-H activation.     

A Poincaré Cone Condition in the Poincaré Group

Ben Arous and Gradinaru (Potential Anal 8(3):217–258, 1998) described the singularity of the Green function of a general sub-elliptic diffusion. In this article we first adapt their proof to the more general context of a hypoelliptic diffusion. In a second time, we deduce a Wiener criterion and a Poincaré cone condition for a relativistic diffusion with values in the Poincaré group (i.e the group of affine direct isometries of the Minkowski space-time).     

Rheological properties of starch suspensions using a rotational rheometer fitted with a starch stirrer cell

The rheological properties of a starch suspension are usually studied through two viscosity measurements-pasting behavior and flow behavior of the resulting starch pastes-performed separately with two different tools and demanding rather high starch concentrations (6–10 wt %). This study focused on the feasibility of using a rheometer fitted with a starch stirrer cell to characterize, in a single experiment, the starch suspension’s behavior during and after pasting, all the while involving only low concentrations (2–4 wt %), more representative of a real-food context. A calibration of the starch stirrer cell in comparison to the coaxial cylinders one was done using model fluids (Newtonian and shear-thinning). A link between torque, rotational speed, and rheological properties was determined through two recalculated conversion factors (shear rate and shear stress). An operating diagram was then set indicating the laminar flow and good sensitivity domain for this cell. The accuracy of those constants to starch suspensions in the concentration range 2–4 wt % was demonstrated. The pasting behaviors of 2 wt % starch suspensions were followed successfully at two selected shear rates (13.5 and 135 s^?1). The impact of the level of turbulence on the profiles obtained was stressed, a result that is not limited to low-concentration starch suspensions. Finally, the method developed was used to compare the pasting behaviors of 2 wt % native and modified waxy maize starch suspensions.