Influence of extra-framework cations on the adsorption properties of X-faujasite systems: microcalorimetry and molecular simulations

Isotherms and differential enthalpies of adsorption are obtained for nitrogen at ambient temperature on monovalent (Li(+), Na(+), K(+)) and divalent (Ca(2+), Ba(2+), Sr(2+), Mn(2+)) substituted X-faujasite systems by microcalorimetry measurements. These experimental data are compared with those obtained by combining grand canonical Monte Carlo simulations and newly derived force fields for describing the interactions between the extra-framework cations and the adsorbates obtained from a simple model based only on the intrinsic properties of the cations. It is the first time that such good qualitative agreement is reported between experiment and simulation for a series of both monovalent and divalent cations.     

Modeling the concentration dependence of the methanol self-diffusivity in faujasite systems: comparison with the liquid phase

Molecular dynamics simulations were performed to understand further the concentration dependence of the self-diffusion of methanol in the faujasite zeolite systems. The evolution of the self-diffusivity was investigated as a function of coverage for DAY and NaY systems to study the effect of both the pore confinement and the presence of the extraframework cations within the supercage. It was found that the self-diffusivity decreases with loading for DAY, whereas for NaY it passes through a maximum at intermediate coverage, in agreement with pulse-field gradient NMR and quasi elastic neutron scattering data reported in similar systems. The activation energies of the methanol diffusion corresponding to a combination of both intra- and intercage motions were evaluated as a function of the coverage. The simulated trends are interpreted on the basis of the predominant interactions which take place in both systems. Finally, the preferential arrangement of the adsorbate molecules are provided and compared with those simulated in the liquid phase. For the fully loaded materials, it was seen that the methanol molecules form a one-dimensional hydrogen-bonded chain along the channels in DAY whereas only dimers are present in NaY.     

Cation migration upon adsorption of methanol in NaY and NaX faujasite systems: a molecular dynamics approach

Molecular dynamics simulations have been carried out to address the question of cation migration upon adsorption of methanol in NaY and NaX faujasite systems as a function of the loading. For NaY, it has been shown that, at low and intermediate loadings, SII cations can migrate toward the center of the supercage due to strong interactions with the adsorbates, followed by a hopping of SI' from the sodalite cage into the supercage to fill the vacant SII site. A SI' cation can also migrate across the double six ring and takes a SI' vacant position. SI cations mainly remain trapped in their initial sites whatever the loading. At high loading, only limited motions are observed for SII cations due to steric effects induced by the presence of adsorbates within the supercage. For NaX, the SIII' cations which occupy the most accessible adsorption sites are significantly moving upon coordination to the methanol molecules; the extent of this mobility exhibits a maximum for 48 methanol molecules per unit cell before decreasing at higher loadings due to steric hindrance. In addition, the SI' and SII cations remain almost trapped in their initial sites whatever the loading. Indeed, the most probable migration mechanism involves SIII' cation displacements into nearby SIII' sites.     

Efficient One‐Pot Synthesis of a Densely Functionalized Tetrahydropyridine in the Presence of [1,1′‐Binaphthalene]‐2,2′‐diol/Indium(III) Chloride (binol/InCl3) or Simple Brønsted Acids as Catalysts

The highly functionalized tetrahydropyridine 4 was obtained in an indium(III) chloride catalyzed multi‐component reaction from benzaldehyde, 4‐methoxyaniline, and ethyl acetoacetate (=ethyl 3‐oxobutanoate) in the presence of [1,1′‐binaphthalene]‐2,2′‐diol (binol). It was found that binol played a beneficial role in this reaction, allowing a substantial decrease of the amount of indium salt. Also, simple organic Brønsted acids may serve as effective organocatalysts in this process.     

Guest‐Assisted Proton Conduction in the Sulfonic Mesoporous MIL‐101 MOF

Post‐synthesis modification of MIL‐101(Cr)‐NO₂ was explored in order to decorate the organic backbone by propyl‐sulfonic groups, with the aim to incorporate mobile and acidic protons for solid‐state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10^?3 S cm^?1. Propitiously, the impregnation of the material by strong acidic molecules (H₂SO₄) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10^?1 S cm^?1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.     

Novel (R)-(+)-limonene-derived ligands: synthesis and application in asymmetric transfer hydrogenations

(R)-(+)-Limonene was transformed into mono-N-tosylated-1,2-diamine derivatives using an N-tosylaziridination procedure followed by sodium azide treatment and reduction on Pd/C. The ligands obtained proved effective in the asymmetric transfer hydrogenation protocol on aromatic ketones.     

Synthesis of new mono-N-tosylated diamine ligands based on (R)-(+)-limonene and their application in asymmetric transfer hydrogenation of ketones and imines

A synthetic procedure leading to the preparation of a new family of enantiopure mono-N-tosylated-1,2-diamines derived from (R)-(+)-limonene is described. (+)-Limonene was transformed into the appropriate N-tosyl derivative using N-tosylaziridination based on chloramine-T trihydrate. Subsequent ring opening by sodium azide afforded the corresponding isomeric azides. Finally, reduction of the azide function gave enantiomerically pure mono-N-tosylated-1,2-diamines. The ligands obtained proved to be effective in the asymmetric transfer hydrogenation protocol on aromatic ketones and imines.     

Coumarinylmethyl Caging Groups with Redshifted Absorption

The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron‐donating groups in the 7 position and electron‐withdrawing groups in the 2‐, and 2‐ and 3 positions. In particular, we showed that the diethylamino‐thiocoumarylmethyl and the diethylamino‐coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470–500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue‐cyan light sources, respectively.     

Formation of a Single-Crystal Aluminum-Based MOF Nanowire with Graphene Oxide Nanoscrolls as Structure-Directing Agents

An innovative strategy is proposed to synthesize single-crystal nanowires (NWs) of the Al³⁺ dicarboxylate MIL-69(Al) MOF by using graphene oxide nanoscrolls as structure-directing agents. MIL-69(Al) NWs with an average diameter of 70±20 nm and lengths up to 2 μm were found to preferentially grow along the [001] crystallographic direction. Advanced characterization methods (electron diffraction, TEM, STEM-HAADF, SEM, XPS) and molecular modeling revealed the mechanism of formation of MIL-69(Al) NWs involving size-confinement and templating effects. The formation of MIL-69(Al) seeds and the self-scroll of GO sheets followed by the anisotropic growth of MIL-69(Al) crystals are mediated by specific GO sheets/MOF interactions. This study delivers an unprecedented approach to control the design of 1D MOF nanostructures and superstructures.