Functionalized gold magic clusters: Au25(SPhNH2)17.

New Au(25) nanoclusters stabilized by heterotopic 4-aminothiophenolate ligands (HSPhNH(2)) have been isolated with a yield of ~70%. The nanoclusters formula determined by ESI-MS is Au(25)(SPhNH(2))(17), with the 18(th) position occupied by an amine or DMF molecules to close their electronic shell.

Absolute molecular sieve separation of ethylene/ethane mixtures with silver zeolite A.

Absolute ethylene/ethane separation is achieved by ethane exclusion on silver-exchanged zeolite A adsorbent. This molecular sieving type separation is attributed to the pore size of the adsorbent, which falls between ethylene and ethane kinetic diameters.

Combinatorial synthesis and characterization of metal-open frameworks in mild and friendly conditions: application to CO2 adsorption.

Combinatorial screening using precipitation methods at room temperature can lead to a great diversity of carboxylate based Metal Organic Frameworks (MOFs) including already known or original porous solids. The investigation of the synthesis of MOFs in different solvent and solvent mixtures includes the use of solvents such as alcohols and tetrahydrofuran (THF) which would greatly facilitate large scale production. We also show the application of Principal Component Analysis (PCA) and clustering techniques on large libraries of XRD diffraction files in order to identify classes of similar phases and peculiar phases. The combinatorial screening of 105 samples in the La/btc system has led to the identification of two phases which are solvent depending. On the La(btc) compound, the CO2 adsorption measurements reveal a guest-host interactions as supported by XRD phase transformation upon thermal treatment. The mass transport can be assigned to a "single file diffusion" regime due to the one dimensional channel porous structure associated to small pore size.

Engineering MIL-53(Al) flexibility by controlling amino tags.

The flexibility of MIL-53(Al) can be tuned by adjusting the ratio of terephthalate and 2-amino terephthalate linkers incorporated into the framework during hydrothermal synthesis.

Amino acid functionalized metal-organic frameworks by a soft coupling-deprotection sequence.

Covalent post-synthetic modification of a MOF, (In) MIL-68-NH(2), is carried out in a novel fashion to immobilize amino acids within the structure. Solid-phase peptide coupling methodology opens new perspectives for anchoring chiral bio- and catalytically active species. This could facilitate the immobilization of highly active and/or coordinating moieties inside MOF cavities.

Operando study of iridium acetylacetonate decomposition on amorphous silica-alumina for bifunctional catalyst preparation.

The decomposition of iridium acetylacetonate Ir(acac)(3) impregnated on amorphous silica-alumina (ASA) has been investigated by combined thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS) and by in situ X-ray diffraction (XRD). The resulting Ir/ASA hydrotreating catalysts have also been characterized by transmission electron microscopy (TEM). The effects of heating treatments under oxidative, reductive or inert gas flows are compared with each other and with similar experiments on ASA-supported acetylacetone (acacH). It is shown that Ir(acac)(3) undergoes exothermic combustion during calcination in air, leading to agglomerated IrO(2) particles. Conversely, direct reduction involves hydrogenolysis of the acac followed by hydrogenation of the ligand residues to alkanes and water. These two processes are catalyzed by Ir clusters, the gradual growth of which is followed in situ by XRD. The resulting nanoparticles are highly and homogeneously dispersed.

Structures and associated catalytic properties of well-defined nanoparticles produced by laser vaporisation of alloy rods.

Bimetallic clusters, all containing gold, have been produced by laser vaporisation of bulk alloys followed by deposition of the formed clusters onto Al2O3 and TiO2 powders or flat silica supports. This technique allows a narrow size distribution of highly dispersed gold-based nanoparticles on powders and nanocrystalline structured thin films on 2D supports to be obtained. The catalytic performances of the as-obtained AuFe, AuNi, AuTi powdery catalysts have been studied in the PROX reaction and compared with those obtained in the oxidation of CO in the temperature range 25-300 degrees C. By comparing the activities of the different catalysts, it is concluded that the nature of the gold partner directly affects the activity of gold. The following tendency is observed: AuFe and AuNi have rather similar activities, significantly lower than that of AuTi. In this paper, we also present a first attempt to study reactivity of original self-supported systems. We show that significant CO oxidation reactivity can be obtained over unsupported nanoporous AuTi and PdAu thin films. By completely excluding the support effect, unsupported catalysts could provide a way of understanding the relevant catalytic mechanisms more easily.

Hydrated Cs+-exchanged MFI zeolites: location and population of Cs+ cations and water molecules in hydrated Cs6.6MFI from in and ex situ powder X-ray diffraction data as a function of temperature and other experimental conditions.

Extending our previous investigation of dehydrated, Cs-exchanged MFI zeolites (J. Phys. Chem. B 2006, 110, 97-106) to hydrated analogues, we have determined the crystal structures of members of the Cs(6.6)H(0.3)MFI.xH(2)O series, for 0 < x < 28, from synchrotron-radiation powder diffraction data. In the fully hydrated phase, three independent Cs(+) cations and six water molecules are identified in difference Fourier maps. The populations of the cations amount to 2.79/3.40/0.41 Cs/unit cell (uc) for the Cs1/Cs2/Cs3 sites, respectively, and those of the water molecules to 4/4/4/4/8/4 H(2)O/uc for the Ow1/Ow2/Ow3/Ow4/Ow5/Ow6 sites, respectively. Close to water saturation, the Cs3 and Ow6 sites are near each other (approximately 1.44 A) and are not occupied simultaneously. At saturation, Cs cations and water molecules form three interconnected Cs(H(2)O)(n) clusters and one (H(2)O)(4) cluster in the MFI channel system: Cs2(H(2)O)(5) centered at x/y/z approximately -0.018/0.146/0.546 (midway between the intersection and the straight channels), Cs1(H(2)O)(4) centered at approximately 0.056/0.240/0.889 (the zigzag channel openings), Cs3(H(2)O)(2) centered at approximately 0.228/0.25/0.899 (in the zigzag channel), and the (H(2)O)(4) cluster (in the zigzag channel) bonded to Cs1 and Ow1. (H(2)O)(4) and Cs3(H(2)O)(2) exclude each other. The Cs2(H(2)O)(5) clusters are connected through weak Ow5...Ow5' hydrogen bonds (2.88 A) and form polymeric chains in the straight channel direction (010). During progressive hydration this Cs2 cation enlarges its hydration shell, stepwise, from Cs2(H(2)O)(2) to Cs2(H(2)O)(3), to Cs2(H(2)O)(4), and finally to a Cs2(H(2)O)(5) cluster. During the dehydration process, these extraframework species migrate, and it is shown that for varying total H(2)O/uc loadings the individual populations of the Cs(+) cations and H(2)O molecules strongly depend on experimental and measurement (in situ vs ex situ) conditions. The shapes of the channels change also; except for T > 150 degrees C, in all the Cs(6.6)H(0.3)MFI.xH(2)O phases, the straight channel D10R (double 10-ring) pore openings (1.16 < epsilon < 1.23) become strongly elliptical. The framework structure of all the investigated phases conforms to orthorhombic Pnma space group symmetry. Hydration and dehydration in Cs(6.6)MFI are fully reversible processes. From a knowledge of the Cs(+) locations, we are able to estimate, by computer simulations, the positions of H(2)O molecules in Cs(6.6)H(0.3)MFI.28H(2)O. The maximum theoretically possible water loading in an hypothetical and idealized cationless [Cs(6.6)H(0.3)]MFI structure amounts to 48 H(2)O/uc (nine independent water species), which is in fair agreement with existing high-pressure data (47 H(2)O/uc). This value is to be compared with the water saturation capacity obtained in a structural refinement of sealed-tube diffraction data of a proton-exchanged H(6.9)MFI.38H(2)O (seven independent water molecules). In the crystal structure of this H-ZSM-5 phase, the straight channel openings are almost circular (epsilon = 1.08). From this we conclude that the main factor responsible for the flexibility of the MFI framework is the presence of the Cs(H(2)O)(n)() clusters residing in, or close to, the straight channel double 10-rings.

Dehydrated and Cs+-exchanged MFI zeolites: location and population of Cs+ from in situ diffraction data as a function of temperature and degree of exchange.

H-MFI type zeolitic materials of different Si/Al ratios have been completely or partially cesium-exchanged (cesium content ranging from 0.7 to 7.7 Cs/unit-cell (uc)). Examined with synchrotron X-ray powder diffractometry, an anhydrous sample with the Cs6.6H0.3Al6.9Si89.1O192 chemical composition revealed at ambient temperature the presence of five discrete Cs locations: Cs1 located in the channel intersection near a 10-ring window of the zigzag channel; Cs2 and Cs2', both located in the straight channel but 1.23 A apart; Cs3 and Cs3', both located in the zigzag channel and rather close to each other (2.51 A). The populations of the Cs species amounted to 2.61/0.81/1.85/0.86/0.47/uc for Cs1/2/2'/3/3', respectively. The continuous but multimodal nature of the C2 split site is well-described by a joint-probability density function. The 10-ring of the straight channel in the framework is highly elliptical (epsilon = 1.218). The populations for the same sites were also determined at higher temperatures: 131, 237, 344, and 450 degrees C. At 450 degrees C, Cs2' has migrated toward the center of the channel intersection, and the site separation between Cs2 and Cs2' has lengthened to 2.23 A. Using a temperature-controlled laboratory X-ray diffractometer, similar studies were carried out on partially or almost totally Cs-exchanged samples from various sources with differing Cs contents. They show that over the 0.7 to 4 Cs/uc range all the individual Cs populations vary linearly as a function of total Cs/uc present. At higher total Cs/uc content (4 to approximately 7 Cs/uc) solely Cs1 continues to do so. For Cs2+Cs2' and Cs3+Cs3', the variation is almost linear over the whole concentration range. Computer simulations using a 6-exp-1 Buckingham-type atom-atom van der Waals interaction model yield six possible Cs sites in the actual Cs6.6MFI framework structure. Four of them lie very close to those determined from difference Fourier maps using the room temperature data. A fifth one is close to the Cs2' species after thermal migration at 450 degrees C, and the sixth one is close to the center of the channel intersection. However, this latter site is observed experimentally only in the case of hydrated CsMFI phases. In the anhydrous Cs6.6MFI phase at room temperature, the shortest Cs-framework oxygen distance is Cs3'-O25 = 3.08 A, and the next shortest distances are Cs1-O26 = 3.37, Cs2-O11 = 3.34, Cs2'-O22 = 3.47, and Cs3-O20 = 3.34 A. The framework T(Si,Al) sites most involved in these contacts are the T9, T11, T12, T10, and T3 sites. This implies that these sites are prime candidates for Si/Al substitution.