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Catalytic hydrogenation of CO2 into CH4 is an effective method to convert waste CO2 and green hydrogen into clean fuel on a large scale. However, the viability of such process largely relies on the development of highly active heterogeneous catalysts. Here, a tailored methanation catalyst, Co nanoparticles immobilized into a highly porous N-doped carbon matrix, is prepared by the carbonization of a cobalt-based layered zeolitic imidazolate framework (ZIF-L) material under an argon atmosphere. This catalyst displays a specific activity of 22.3 molCH4/gcat.min at 350°C, significantly outperforming a similar catalyst derived from the more conventional ZIF-67 (11.7 molCH4/gcat.min). This is explained by the stabilization of small Co nanoparticles (~20 nm) and by the presence of abundant medium-strength basic sites related to the nitrogen doping in the catalyst prepared from ZIF-L. Notably, the new catalyst shows high stability; no deactivation is observed up to 60 hours on stream.

Multiscale and multitool advanced characterisation of pyrophosphate-stabilised amorphous calcium carbonates allowed building a cluster-based model paving the way for tunable biomaterials.

Molecularly-defined organometallic rhodium phosphine complexes were efficiently heterogenized within a MOF structure without affecting neither their molecular nature nor their catalytic behavior. Phosphine-functionalized MOF-808 served as solid ligand in a series of eight rhodium phosphine catalysts. These MOF-heterogenized molecular catalysts showed activity up to 2100 h-1 for ethylene hydroformylation towards pro-pionaldehyde as sole carbon-containing product. Combined experimental and computational methods applied to this unique MOF-based molecular system allowed unravelling structure and evolution of the Rh active species within the MOF under catalytic conditions, in line with molecular mechanisms at play during the hydroformylation reaction. The MOF-808 designed as a porous crystalline macroligand for well-defined molecular catalysts allows benefiting from molecular-scale understanding of interactions and mechanisms as well as from stabilization through site-isolation and recycling ability.

International audience; The formation of iron phosphide nanoparticles (FexP) is a well‐studied process. It usually uses air‐sensitive phosphorus precursors such as n‐trioctylphosphine or white phosphorus. In this study, we report the synthesis and characterization of a remarkably stable tetrakis(acyl)cyclotetraphosphane, P4(MesCO)4. We demonstrate that this compound can be used as a stoichiometric source of P(0) species in order to synthesize FeP and Fe2P nanoparticles at only 250 °C. This tunable process provides a route to monodisperse nanoparticles with different compositions and crystallinities. We combine X‐Ray photoelectron spectroscopy and atomic pair distribution function (PDF) to study the local order and bonding in the amorphous and crystalline materials. We show that crystalline FeP forms via an intermediate amorphous phase (obtained at a lower temperature) that presents local order similar to that of the crystalline sample. We explore their electrocatalytic properties for the hydrogen evolution reaction (HER) in acidic and neutral electrolytes. In both electrolytes, amorphous FeP is a more efficient catalyst than crystalline FeP, itself more efficient than crystalline Fe2P. Our study paves the way for a more systematic investigation of amorphous metal phosphide phases in electrocatalysis. It also shows the beneficial use of PDF on the highly challenging characterization of amorphous nanomaterials.

Heterogenization of molecular catalysts via their immobilization within extended structures often results in a lowering of their catalytic properties due to a change in their coordination sphere. Metal–organic polyhedra (MOP) are an emerging class of well-defined hybrid compounds with a high number of accessible metal sites organized around an inner cavity, making them appealing candidates for catalytic applications. Here, we demonstrate a design strategy that enhances the catalytic properties of dirhodium paddlewheels heterogenized within MOP (Rh-MOP) and their three-dimensional assembled supramolecular structures, which proved to be very efficient catalysts for the selective photochemical reduction of carbon dioxide to formic acid. Surprisingly, the catalytic activity per Rh atom is higher in the supramolecular structures than in its molecular sub-unit Rh-MOP or in the Rh-metal–organic framework (Rh-MOF) and yields turnover frequencies of up to 60 h–1 and production rates of approx. 76 mmole formic acid per gram of the catalyst per hour, unprecedented in heterogeneous photocatalysis. The enhanced catalytic activity is investigated by X-ray photoelectron spectroscopy and electrochemical characterization, showing that self-assembly into supramolecular polymers increases the electron density on the active site, making the overall reaction thermodynamically more favorable. The catalyst can be recycled without loss of activity and with no change of its molecular structure as shown by pair distribution function analysis. These results demonstrate the high potential of MOP as catalysts for the photoreduction of CO2 and open a new perspective for the electronic design of discrete molecular architectures with accessible metal sites for the production of solar fuels.

Heterogenization of molecular catalysts via their immobilization within extended structures often results in a lowering of their catalytic properties due to a change in their coordination sphere. Metal-organic polyhedra (MOP) are an emerging class of well-defined hybrid compounds with a high number of accessible metal sites organized around an inner cavity, making them appealing candidates for catalytic applications. Here, we demonstrate a design strategy that enhances the catalytic properties of dirhodium paddlewheels heterogenized within MOP (Rh-MOP) and their three-dimensional assembled supramolecular structures, which proved to be very efficient catalysts for the selective photochemical reduction of carbon dioxide to formic acid. Surprisingly, the catalytic activity per Rh atom is higher in the supramolecular structures than in its molecular sub-unit Rh-MOP or in the Rh-metal-organic framework (Rh-MOF) and yields turnover frequencies of up to 60 h

International audience; Bone collagenous extracellular matrix provides a confined environment into which apatite crystals form. This biomineralization process is related to a cascade of events partly controlled by noncollagenous proteins. Although overlooked in bone models, concentration and physical environment influence their activities. Here, we show that collagen suprafibrillar confinement in bone comprising intra- and interfibrillar spaces drives the activity of biomimetic acidic calcium-binding polymers on apatite mineralization. The difference in mineralization between an entrapping dentin matrix protein-1 (DMP1) recombinant peptide (rpDMP1) and the synthetic polyaspartate validates the specificity of the 57-KD fragment of DMP1 in the regulation of mineralization, but strikingly without phosphorylation. We show that all the identified functions of rpDMP1 are dedicated to preclude pathological mineralization. Interestingly, transient apatite phases are only found using a high nonphysiological concentration of additives. The possibility to combine biomimetic concentration of both collagen and additives ensures specific chemical interactions and offers perspectives for understanding the role of bone components in mineralization.

International audience; Ni@SBA-15 monoliths with up to 5 wt.% of Ni were successfully synthetized by means of an original and easy one-pot sol-gel method. Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Temperature-Programmed Reduction (TPR), Pair Distribution Function (PDF) and X-Ray Diffraction (XRD) were used for the structural characterization of the samples. After H2-reduction, those solids exhibited small Ni 0 particles (between 1-3 nm) highly dispersed (one of the highest dispersion reported in the literature to date for 5 wt.% 2 Ni/Silica materials) in strong interaction with the silica support. Scanning Transmission Electron Microscopy in the High Angle Annular Dark Field (STEM/HAADF) mode, chemical mapping by Energy Dispersive X-Ray (EDX) spectroscopy and electron tomography in STEM-HAADF mode highlighted the presence of Ni particles homogeneously distributed, especially in the mesopores. Such confined Ni nanoparticles were shown to be very selective and stable in the dry reforming of methane.

International audience; We evidence the structure-directing role of the PW12O403-polyoxometalate in the synthesis of porphyrinicMOFswhereby it promotes the formation of the kinetic topology. Its immobilization into the MOF is successfully achieved at high temperature yielding the kinetic MOF-525/PCN-224 phases, while prohibiting the formation of the thermodynamic MOF-545 product. A combined experimental and theoretical approach uses differential PDF and DFT calculations along with solid-state NMRto show the structural integrity of the hosted POM andits location in the vicinity of the Zr-based nodes.

International audience; The Keggin-type polyoxometalate (POM) PW12O403– and the catalytic complex Cp*Rh(bpydc)Cl2 (bpydc = 2,2′-bipyridine-5,5′-dicarboxylic acid) were coimmobilized in the Zr(IV) based metal organic framework UiO-67. The POM is encapsulated within the cavities of the MOF by in situ synthesis, and then, the Rh catalytic complex is introduced by postsynthetic linker exchange. Infrared and Raman spectroscopies, 31P and 13C MAS NMR, N2 adsorption isotherms, and X-ray diffraction indicate the structural integrity of all components (POM, Rh-complex and MOF) within the composite of interest (PW12,Cp*Rh)@UiO-67. DFT calculations identified two possible locations of the POM in the octahedral cavities of the MOF: one at the center of a UiO-67 pore with the Cp*Rh complex pointing toward an empty pore and one off-centered with the Cp*Rh pointing toward the POM. 31P–1H heteronuclear (HETCOR) experiments ascertained the two environments of the POM, equally distributed, with the POM in interaction either with the Cp* fragment or with the organic linker. In addition, Pair Distribution Function (PDF) data were collected on the POM@MOF composite and provided key evidence of the structural integrity of the POM once immobilized into the MOF. The photocatalytic activity of the (PW12,Cp*Rh)@UiO-67 composite for CO2 reduction into formate and hydrogen were evaluated. The formate production was doubled when compared with that observed with the POM-free Cp*Rh@UiO-67 catalyst and reached TONs as high as 175 when prepared as thin films, showing the beneficial influence of the POM. Finally, the stability of the composite was assessed by means of recyclability tests. The combination of XRD, IR, ICP, and PDF experiments was essential in confirming the integrity of the POM, the catalyst, and the MOF after catalysis.

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

International audience; We report on the in situ analysis of the growth process of carbon nanostructures catalyzed by Ru nanoparticles using syngas, a mixture of hydrogen and CO, as the carbon source at a medium temperature (500 °C). The structural modifications of the dual nanotube/nanoparticle system and the general dynamics of the involved processes have been directly followed during the growth, in real time and at the atomic scale, by transmission electron microscopy in an environmental gas cell at atmospheric pressure. After a reduction step under hydrogen and syngas, the particles became very active for the carbon growth. The growth rate is independent of the particle size which mainly influences the nanotube wall thickness. Other subtle information on the general behavior of the system has been obtained, as for instance the fact that the regular changes in the direction of the particle originate generally from the particle shape fluctuation. The main result is the evidence of a new growth mode in relation to the presence and the high instability of the ruthenium carbide phase which acts as a carbon reservoir. For the first time, a relaxation oscillation of the growth rate has been observed and correlated with the metal–carbide structural transition at the particle sub-surface.

Mesoporous TiO2 materials have been prepared by an aerosol process, which leverages on the acetic acid-mediated sol-gel chemistry and on the evaporation-induced self-assembly phenomenon to obtain materials with high specific surface area and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when the calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions lead to the progressive destruction of the mesostructured, concomitant with a progressive drop of textural properties and with the crystallization of larger anatase domains. The mesoporous TiO2 material calcined at 350°C (specific surface area = 260 m².g-1; pore volume = 0.36 cm³.-1; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO2 nanoparticles, and subsequently annealed in air. It is shown that the presence of RuO2 nanoparticles and subsequent annealing provoke further intense modification of the texture and crystallinity of the TiO2 materials. In addition to a drop in the textural parameters, a RuO2-mediated crystallization of rutile TiO2 is highlighted at temperature as low as 250°C. After an in situ reduction in H2, the catalysts containing TiO2 rutile and relatively small RuO2 crystals showed the highest activity in the methanation of CO2.

International audience; Among the inorganic compounds, many oxides and sulfides are known to be semiconductors. At the crossroads of these two families, oxysulfide MxOySz compounds were much less investigated because they are scarce in nature and complex to synthesize. Amongst them, lanthanide oxysulfide Ln2O2S (Ln = lanthanide) are indirect bandgap semiconductors, with wide gaps, except Ce2O2S. (Gd,Ce)2O2S anisotropic nanoparticles with hexagonal structure were obtained over the whole composition range and exhibit colors varying from white to brown with increasing Ce concentration. Bandgap engineering is thus possible, from 4.7 eV for Gd2O2S, to 2.1 eV for Gd0.6Ce1.4O2S, while the structure is preserved with a slight lattice expansion. Surprisingly, due to the limited thickness of the lamellar nanoparticles, the bandgap of the nanoparticles is direct as validated by density functional theory on slabs. The fine control of the bandgap over a wide range, solely triggered by the cation ratio, is rarely described in the literature and highly promising for further development of this class of compounds. We propose a multi-regime mechanism to rationalize the bandgap engineering over the whole composition range. This should inspire the design of other bimetallic nanoscaled compounds, in particular in the field of visible light photocatalysis.

Natural abundance 43Ca solid state NMR experiments are reported for the first time at ultra-high magnetic field (35.2 T) on a series of Ca-(pyro)phosphate and Ca-oxalate materials, which are of biological relevance in relation to biomineralization processes and the formation of pathological calcifications. The significant gain in both sensitivity and resolution at 35.2 T leads to unprecedented insight into the structure of both crystalline and amorphous phases.

The high CO 2 methanation activity of Ru/TiO 2 catalysts prepared by mixing both anatase and rutile TiO 2 as a support is described, focusing on mild reaction temperature (50–200 °C). The specific catalyst design elucidated the impact of the support mixing. Pre-synthesized, monodispersed 2 nm-RuO 2 nanoparticles were used to serve as precursors for active metallic Ru responsible for the CO 2 hydrogenation reaction. Pure TiO 2 supports with different crystallinity (anatase and rutile) were either prepared in the laboratory or obtained from commercial providers, mixed, and used as supports in different ratios. The mixing was also done at different stages of the catalyst preparation, i.e. before RuO 2 deposition, before annealing or after annealing. Our study uncovers that the interaction between the RuO 2 nanoparticles and the anatase and rutile TiO 2 phase during the annealing step dictates the performance of the Ru/TiO 2 methanation catalysts. In particular, when beneficial effects of support mixing are obtained, they can be correlated with RuO 2 migration and stabilization over rutile TiO 2 through epitaxial lattice matching. Also, support mixing can help prevent the sintering of the support and the trapping of the active phase in the bulk of the sintered support. On thermally stable TiO 2 supports, however, it appears clearly that the sole presence of rutile TiO 2 support is sufficient to stabilize Ru in its most active form and to prepare a catalyst with high specific activity.

International audience; Processing strategies for the synthesis of hybrid materials stand as relevant ways to modulate the particle size and morphology. We present herein the use of a continuous high temperature-high pressure (HT-HP) process for the synthesis of a new cerium based metal-organic framework (MOF). The HT-HP harsh thermodynamic synthesis conditions lead to MOF nanostructures exhibiting the same phase as for microparticles obtained under conventional batch solvothermal conditions but in exceptional much shorter residence times, opening avenues towards production scaling-up. The HT-HP process also tailors down the size of the particles, which still presents a major issue for most MOF applications.

International audience; Herein we discuss band gap modification of MIL-125, a TiO2/1,4-benzenedicarboxylate (bdc) metal-organic framework (MOF). Through a combination of synthesis and computation, we elucidated the electronic structure of MIL-125 with aminated linkers. The band gap decrease observed when the monoaminated bdc-NH2 linker was used arises from donation of the N 2p electrons to the aromatic linking unit, resulting in a red-shifted band above the valence-band edge of MIL-125. We further explored in silico MIL-125 with the diaminated linker bdc(NH2)(2) and other functional groups (-OH, -CH3, -Cl) as alternative substitutions to control the optical response. The bdc-(NH2)2 linking unit was predicted to lower the band gap of MIL-125 to 1.28 eV, and this was confirmed through the targeted synthesis of the bdc-(NH2)(2)-based MIL,-125. This study illustrates the possibility of tuning the optical response of MOFs through rational functionalization of the linking unit, and the strength of combined synthetic/computational approaches for targeting functionalized hybrid materials.

The synthesis and the characterization of a new octanuclear carboxylated titanium oxo-cluster [Ti8O10(OOCR)(12)] [R = CH(CH3)(2) and CCl3] is reported. The structure was characterized by single-crystal X-ray diffraction. It consists in four vertices-linked pairs of edge-sharing TiO6 octahedra, presenting 2 and 3 oxygen atoms. O-17 and C-13 liquid state NMR was performed with results in full accordance with the structure determined by X-ray diffraction. During synthesis, solvothermal conditions and a large excess of carboxylic acid allow to remove all alkoxo ligands of the titanium alkoxide precursor and lead to stable purely carboxylate clusters. This family of clusters can therefore be considered as interesting SBUs to elaborate new metal-organic frameworks.

© 2016 American Chemical Society. Ruthenium catalysts supported on TiO2 have been shown to have competitive activity and selectivity for the methanation of CO2. In particular, a catalyst using preformed RuO2 nanoparticles deposited on a TiO2 support showed competitive performances in a previous study. In this work, ambient-pressure X-ray photoelectron spectroscopy was employed to determine the chemical state of this catalyst under reaction conditions. The active state of ruthenium was found to be the metallic one. Surface adsorbates were monitored in the steady state, and CHx species were found to be favored over adsorbed carbon monoxide at increasing temperatures.

International audience; The catalytic hydrogenation of CO2 is a relevant strategy for mitigating CO2 emissions and its applicability relies on our ability to prepare catalysts that are highly active under mild conditions. Understanding and improving these tailored catalysts requires innovative materials synthesis routes and advanced methods of characterization. In this study, mono-dispersed 2 nm RuO2 nanoparticles were prepared as a stable colloidal suspension and deposited onto different titania supports by impregnation. Supported RuO2 nanoparticles are homogeneously dispersed at the surface of the titania supports. Then, upon annealing and reduction, metallic Ru nanoparticles are obtained, which are active in the hydrogenation of CO2 to CH4. However, depending on the crystal structure of the different TiO2 supports (anatase, rutile, and a mixture of both), the catalysts exhibited drastically diverse catalytic performances. An array of characterization tools (N2-physisorption, H2-chemisorption, HR-TEM, STEM-HAADF, 3D tomographic analysis, XRD, and XPS) was used to unravel the origin of this support effect. It appeared that catalytic behaviour was related to profound morphological changes occurring during the annealing step. In particular, advanced electron microscopy techniques allow visualisation of the consequences of RuO2 nanoparticle mobility onto titania. It is shown that RuO2 sinters heavily on anatase TiO2, but spreads and forms epitaxial layers onto rutile TiO2. On anatase, large Ru chunks are finally obtained. On rutile, the formation of a particular “rutile-TiO2/RuO2/rutile-TiO2 sandwich structure” is demonstrated. These phenomena – along with the relative thermal instability of the supports – explain why the catalysts based on the commercial P25 titania support outperform those based on pure crystalline titania. The study opens new perspectives for the design of highly active CO2 methanation catalysts.

K2[CrF5·H2O] is monoclinic: a = 9.6835(3) A, b = 7.7359(2) A, c = 7.9564(3) A, β = 95.94(1)°, Z = 4, space group C2/c (no 15). Its crystal structure was solved from its X-ray powder pattern recorded on a powder diffractometer, using for the refinement the Rietveld method. It is built up from isolated octahedral [CrF5·OH2]2− anions separated by potassium cations. The dehydration of K2[CrF5·H2O] leads to anhydrous orthorhombic K2CrF5: a = 7.334(2) A, b = 12.804(4) A, c = 20.151(5) A, Z = 16, space group Pbcn (no 60), isostructural with K2FeF5.

The title polyanion is the first hybrid borophosphate-phenylphosphonate polyoxometalate. It was structurally characterized as its imidazolium salt, (C(3)N(2)H(5))(5)[Mo(12)O(30)(BPO(4))(2)(O(3)P-Ph)(6)].H(2)O (monoclinic, P2(1)/c, a = 22.120(3) A, b = 13.042(2) A, and c = 32.632(4) A, beta = 101.293(3) degrees ), which was synthesized hydrothermally from imidazole, molybdenum oxide and metal, and boric, phosphoric, and phenylphosphonic acids. The anion is the second example of a new class of polyoxometalates that resemble Dawson anions but where the two pole caps of three edge-sharing MoO(6) octahedra in the latter are replaced by other units, in this case tetrahedral borate sharing corners with three phenylphosphonic groups, [(OB)(O(3)P-Ph)(3)]. The 12 molybdenum atoms forming the two equatorial belts of the cluster are of mixed-valence, five are Mo(V) and seven are Mo(VI), and the resulting five electrons are delocalized. Four of these electrons are paired according to the temperature dependence of the magnetic susceptibility. The new compound is soluble in a mixture of water and pyridine (in equal volumes) as well as in nitromethane, and the anions are intact in these solutions.

Two new compounds containing the title diphosphono-polyoxometalate anion and diprotonated ethylenediamine (enH(2)) or piperazine (ppzH(2)) countercations have been hydrothermally synthesized and structurally characterized ((enH(2))(4)[Mo(7)O(16)(O(3)PCH(2)PO(3))(3)].7H(2)O, triclinic, P(-)1, Z = 2, a = 10.3455(7) A, b = 13.136(1) A, and c = 20.216(3) A, alpha = 93.247(6) degrees, beta = 96.434(6) degrees, and gamma = 111.900(6) degrees; (ppzH(2))(4)[Mo(7)O(16)(O(3)PCH(2)PO(3))(3)].8H(2)O, triclinic, P(-)1, Z = 2, a = 13.255(2) A, b = 13.638(2) A, and c = 16.874(4) A, alpha = 93.20(2) degrees, beta = 101.27(2) degrees, and gamma = 105.87(1) degrees). The anion is a ring of three pairs of edge-sharing octahedra of Mo(V)O(6) (with Mo(V)-Mo(V) bonds) that share corners with each other. The diphosphonate groups connect the pairs at the periphery. The ring is "capped" by a tetrahedron of Mo(VI)O(4). According to magnetic measurements, the compounds are diamagnetic.

Two fluorinated gallium phosphates, Ga4(PO4)4F1.33(OH)0.67·1.5NC5H12·0.5H3O·0.5H2O (ULM-16) and Ga9(PO4)8F7.3(OH)0.2·4NC5H12·0.5H3O·3.5H2O (MIL-46), have been hydrothermally synthesized by varying the fluorine amount in the presence of cyclopentylamine as structure-directing agent (at 180 °C for 3 days). Their structures were determined by means of single-crystal X-ray diffraction. The first compound (obtained with low fluorine concentration) is isostructural to the gallium phosphate ULM-16 previously prepared with cyclohexylamine. Its three-dimensional framework is built up from the connection by corner sharing of the hexameric units Ga3(PO4)3F2 together with the tetramer Ga2(PO4)2 and consists of channels bound by 16 polyhedra inserting the protonated cyclopentylamine. The second phase (prepared with high fluorine concentration) exhibits a new three-dimensional topology based on the condensation by corner sharing of the identical hexameric building block Ga3(PO4)3F2 with a pentameric species Ga3(PO4)2F4...

International audience; Ru/gamma-Al2O3 catalysts were prepared using three different methods: wet impregnation, colloidal method and microemulsion. Ru-supported nanoparticles with different average sizes and distribution of sizes were obtained. The catalysts were tested in ammonia synthesis under mild reaction conditions, namely low temperature (100 degrees C) and low pressure (4 bar), and characterized by N-2 adsorption, XRD, XPS, TEM and TPR techniques. The results indicate that a good catalytic performance can be achieved by Ru supported nanoparticles fulfilling two requirements: (i) a relatively high average size (despite the usual assertion that only small particles are required) and (ii) a broad distribution of sizes that ensures the presence of both small particles, containing highly active sites, and large nanoparticles, which are shown to promote the reaction on small particles. This promotion results from a cooperative effect between small and large nanoparticles in good contact, which also allows keeping a highly reduced surface of ruthenium. It is proposed that, under mild reaction conditions, large Ru nanoparticles promote the ammonia synthesis reaction by allowing a more effective activation and transfer of hydrogen atoms, able to hydrogenate strongly adsorbed nitrogen atoms, and thus to release active sites for the activation of N2. (c) 2013 Elsevier B.V. All rights reserved.

Ga4(PO4)4F4·N4C24H60 or MIL-35 is a new layered fluorinated gallium phosphate obtained by mild hydrothermal synthesis using 1,12-diaminododecane as structure-directing agent. It crystallizes in the triclinic space group P1, a=539.3(2) pm, b=981.3(7) pm, c=1928.5(7) pm, α=80.67(6)°, β=88.78(5)°, γ=89.86(7)°, V=1006.9(9)×106 pm3, Z=1 and the refinements from single-crystal X-ray diffraction analysis converge to R1(F)=0.0622 and wR2(F2)=0.1346 for 5044 reflections with I>2σ(I). The inorganic sheets, stacked along [0 0 1] consist of GaO4F2 octahedra connected with PO4 tetrahedra interleaved by 1,12-diaminododecane molecules. The angle formed by the inorganic layer and the diamine molecule is around 52°.

International audience; For 25 years, Chemistry of Materials has been clearly providing a key forum to chemists, physicists, and engineers interested in materials preparation and characterization, in the search of unique physical properties and processing of innovative materials and devices. This short review presents a discussion on some recent advances in this field, illustrated with a few selected examples related to three of our main research areas: the synthesis of single nano-objects and the processing of porous and hierarchically structured materials and hybrid nanocomposite materials. A strong emphasis is also given to the need to realize a successful marriage between materials chemistry and smart processing. These cross-cutting approaches in the vein of bioinspired synthesis strategies are allowing the development of complex systems of various shapes with perfect mastery at different length scales of composition, structure, porosity, functionality, and morphology. These ``integrative strategies'', where all aspects of materials science are coupled, open a land of opportunities to tailor-made advanced inorganic and hybrid materials. Some of them are already impacting numerous societal concerns and industrial applications.

International audience; The reactions of titanium alkoxides with a large excess of different carboxylic acids under nonhydrolytic conditions leads to the reproducible formation of well-defined nano-building units (NBUs) with the formula [Ti8O8(OOCR)16] [R = C6H5, C(CH3)3, CH3]. The structures of these titanium–oxo–carboxylate clusters have been determined by crossing different characterization techniques and methodologies (single-crystal X-ray diffraction, and 13C and 1H solid state NMR spectroscopy).The solubility and transferability of these clusters in common solvents can be tuned by selecting the nature of the organic ligand. Indeed, a robust post-modification of the carboxylate ligands can be done by trans- esterification reactions on the titanium–oxo clusters. These reactions keep the integrity of the octameric titanium–oxo core intact, while completely exchanging the organic shell of the cluster.In this study, one- and two-dimensional solid state NMR and relaxation measurements have been highly complementary to the thermal agitation obtained by crystallography. It has also been evidenced that entrapping of small molecules can be easily done. This is an interesting feature for storage and catalysis.

New hybrid star-like macromolecular objects have been designed from an inorganic multifunctional platform following two routes. The first one consists of the direct introduction of polymer arms at the surface of the titanium oxo-cluster [Ti16O16(OEt)32] by alkoxide exchange. The second approach corresponds to the growth by Atom Transfer Radical Polymerization (ATRP) of n-butyl acrylate from the macroinitiator [Ti16O16(OEt)26(OCH2CCl3)6]. By crossing different characterization techniques and methodologies (single crystal X-ray diffraction, 13C and 17O NMR and 1H DOSY NMR spectroscopy, Size Exclusion Chromatography), evidence of the formation of such macromolecular compounds is reported.

A new open-framework fluorinated gallium phosphate (MIL-31) containing the Ga9(PO4)9(H2O)(OH)(OH,F)4 5− anion was hydrothermally synthesized by using long alkyl chain diamines (C9 and C10) as structure-directing agents; its crystal structure is built up from hexameric units and exhibits large one-dimensional hexagonal channels delimited by 18-rings.

International audience; The reactions of titanium alkoxides with a large excess of different carboxylic acids under nonhydrolytic conditions leads to the reproducible formation of well‐defined nano‐building units (NBUs) with the formula [Ti8O8(OOCR)16] [R = C6H5, C(CH3)3, CH3]. The structures of these titanium–oxo–carboxylate clusters have been determined by crossingdifferent characterization techniques and methodologies (single‐crystal X‐ray diffraction, 13C and 1H NMR spectroscopy, and FTIR spectroscopy). These NBUs are obtained in high yields and, since all the alkoxo ligands have been removed by using solvothermal‐synthesis conditions, they present better stability upon hydrolysis than the often reported alkoxo–carboxylate–titanium–oxo clusters [TinO2n–x/2–y/2(OR′)x(OOCR)y] (n ≥ 2; x ≥ 1; y ≥ 1). In addition, the solubility and transferability of these clusters in common solvents can be tuned by selecting the nature of the organic ligand. Moreover, we also report for the first time, a robust post‐modification of the carboxylate ligands by transesterification reactions on the titanium–oxo clusters. These reactions keep the integrity of the octameric titanium–oxo core intact, while completely exchanging the organic shell of the cluster. This family of [Ti8O8(OOCR)16] clusters, which present 16 points of extension, a symmetric shape, and the ability to be post‐modified with conservation of the core structure, can therefore be considered as interesting NBUs to form new metal–organic frameworks.

RuO 2 -based mesoporous thin films of optical quality are synthesized from ruthenium-peroxo-based sols using micelle templates made of amphiphilic polystyrene-polyethylene oxide block copolymers. The mesoporous structure and physical properties of the RuO 2 films (mesoporous volume: 30%; pore diameter: ∼30 nm) can be controlled by the careful tuning of both the precursor solution and thermal treatment (150―350 °C). The optimal temperature that allows control of both mesoporosity and nanocristallinity is strongly dependent on the substrate (silicon or fluorine-doped tin oxide). The structure of the resulting mesoporous films are investigated using X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. Mesoporous layers are additionally characterized by transmission and scanning electron microscopy and ellipsometry while their electrochemical properties are analyzed via cyclic voltammetry. Thick mesoporous films of ruthenium oxide hydrates, RuO 2 · xH 2 O, obtained using a thermal treatment at 280 °C, exhibit capacitances as high as 1000 ± 100 F g ―1 at a scan rate of 10 mV s ―1 , indicating their potential application as electrode materials.

The description of three titanium oxo-clusters and their use as inorganic components of hybrid organic-inorganic materials are reported. The first approach consists to add titanium oxo-clusters, [Ti6O4(C6H5COO)8(OPrn)8], in an ORMOCER⊗ based hybrid medium. Nano-sized titanium oxo-clusters combined with the chemical nature of the components, allow the tuning of the optical properties, especially the refractive index. The second approach consists to associate functionalized titanium oxo-clusters to elaborate hybrid materials with perfectly defined inorganic domains. The more relevant example of titanium oxo-cluster to build hybrid networks from nano-building blocks is the oxo-cluster [Ti16O16(OEt)32]. Indeed, the nature and the number of functional groups at the surface of these metallic oxo-clusters can be tuned in order to generate cross-linking agents of organic polymers. The studies of the structure-property relationships of the resulting nanocomposites have been investigated. Finally the structure of a purely carboxylate oxo-clusters is briefly described. This new family of stable oxo-clusters opens the way for the production of original hybrid compounds.

A new aluminophosphate, MIL-34, is investigated from its as-synthesized structure to its calcined microporous form. Single-crystal X-ray diffraction measurements on the as-synthesized MIL-34 (Al(4)(PO(4))(4)OH x C(4)H(10)N, space group P-1, a = 8.701(3) A, b = 9.210(3) A, c = 12.385(3) A, alpha = 111.11(2) degrees, beta = 101.42(2) degrees, gamma = 102.08(2) degrees, V = 863.8(4) A(3), Z = 2, R = 3.8%) reveal a 3-D open framework where Al atoms are in both tetrahedral and trigonal bipyramidal coordinations. It contains a 2-D pore system defined by eight rings where channels along [100] cross channels running along [010] and [110]. CBuA molecules are trapped at their intersection. (27)Al, (31)P, and (1)H MAS NMR spectroscopies corroborate these structural features. Calcination treatments of a powder sample of the as-synthesized MIL-34 indicate its transformation into the related template-free structure that is stable up to 1000 degrees C. Lattice energy minimizations are then used in order to anticipate the crystal structure of the calcined MIL-34, starting with the knowledge of the as-synthesized structure exclusively. Energy minimizations predict a new regular zeotype structure (AlPO(4), space group P-1, a = 8.706 A, b = 8.749 A, c = 12.768 A, alpha = 111.17 degrees, beta = 97.70 degrees, gamma = 105.14 degrees, V = 846.75 A(3), Z = 2) together with a thermodynamic stability similar to that of existing zeotype AlPOs. Excellent agreement is observed between the diffraction pattern calculated from the predicted calcined MIL-34 and the experimental X-ray powder diffraction pattern of the calcined sample. Finally, the atomic coordinates and cell parameters of the calcined MIL-34 predicted from the simulations are used to perform the Rietveld refinement of the calcined sample powder pattern, further corroborated by (27)Al and (31)P NMR measurements. This unique combination of experiment and simulation approaches is an interesting and innovative strategy in materials sciences, where simulations articulate the prediction of a possible template-free framework from its as-synthesized templated form. This is especially valuable when straightforward characterizations of the solid of interest with conventional techniques are not easy to carry out.

Publisher Summary This chapter discusses the hydrothermal synthesis and the structure characterization of a novel microporous aluminum phosphate Al 4 (PO 4 ) 4 (OH), NC 4 H 10 , labeled MIL-34. The open framework is built up from interconnected tunnels bounded by 8-membered rings. The cyclobutylamine molecules that are used as structure-directing agent are found at the intersection of the 8-ring channels.

Highly stable suspensions of monodispersed ruthenia nanoparticles have been prepared via a sustainable aqueous oxidative pathway. The nanoparticles (2 nm) have been thoroughly characterized by TEM, XRD, XPS, MS-TGA and thermodiffraction. The addition of hydrogen peroxide in the RuCl3 solution provokes a fast oxidation of Ru(III) ions into Ru(IV). This increases the rate of the hydrolysis/condensation reactions and further promotes the nucleation over the growth of the particles. The very high stability conditions of the colloidal suspension have been studied. This aqueous one-step process, which uses no organic solvent or toxic pollutant additive, is quick and produces calibrated ruthenia nanoparticles in high yields. It presents a green alternative to the preparation and use of ruthenia. As examples, two applications are presented. In the first, RuO2 coatings have been tested for their electrical capacitance. In the second, RuO2/TiO2 catalysts, prepared from the controlled deposition of ruthenia nanoparticles on TiO2 particles, have been proven to be highly effective for the production of methane from CO2.

“Chimie douce” based strategies allow, through the deep knowledge of materials chemistry and processing, the birth of the molecular engineering of nanomaterials. This feature article will highlight some of the main research accomplishments we have performed during the last years. We describe successively the design and properties of: sol–gel derived hybrids, Nano Building Blocks (NBBs) based hybrid materials, nanostructured porous materials proceeds as thin films and ultra-thin films, aerosol processed mesoporous powders and finally hierarchically structured materials. The importance of the control of the hybrid interfaces via the use of modern tools as DOSY NMR, SAXS, WAXS, Ellipsometry that are very useful to evaluate in situ the hybrid interfaces and the self-assembly processes is emphasized. Some examples of the optical, photocatalytic, electrochemical and mechanical properties of the resulting inorganic or hybrid nanomaterials are also presented.

A new open-framework fluorinated gallium phosphate (MIL-31) containing the Ga9(PO4)9(H2O)(OH)(OH,F)4 5− anion was hydrothermally synthesized by using long alkyl chain diamines (C9 and C10) as structure-directing agents; its crystal structure is built up from hexameric units and exhibits large one-dimensional hexagonal channels delimited by 18-rings.

This PhD thesis is part of a larger European ITN project (Photo4Future) dealing with improvement of the use of sun light for making valuable products through new heterogeneous catalytic photochemical processes. In this context, the synthesis of nanophotocatalysts is essential since their characteristics must be controlled to optimize the process efficiency towards the desired products. Supercritical fluids synthesis approaches (high pressure / high temperature) have proven to be promising for such developments. Combined to microreactors, it is then possible to reach a precise control of material properties, including surfaces. The objectives of this project are (i) to develop synthetic methods for designing new nanophotocatalysts based on titania and nitrides quantum dots, in particular GaN/TiO2 and GaxIn1-xN/TiO2, (ii) to test their photocatalytics efficiency on several model photochemical reactions (oxidation of thiols, trifluoromethylation and amine to imine conversion), both in batch mode and using continuous flow photochemical reactors and (iii) to investigate the scale-up options for increasing the production rates of such nanophotocatalysts., Ce sujet de thèse fait partie d’un projet européen visant à développer l’utilisation de la lumière solaire pour créer des produits à haute valeur ajoutée en utilisant la photochimie catalytique. Dans ce contexte, la synthèse de nanophotocatalyseurs est essentielle car les caractéristiques des nanomatériaux doit être maîtrisées pour optimiser l'efficacité de la réaction. Les méthodes de synthèses utilisant les fluides supercritiques (haute pression / haute température) se sont révélés être des procédés de choix pour de tels développements. Combinés à l’utilisation de microréacteurs, il est alors possible d’accéder à un contrôle fin des propriétés du matériau, notamment celles de surface. Les objectifs de ce projet sont de (i) développer des procédés de synthèse permettant de concevoir de nouveaux nanophotocatalyseurs basés sur l’oxyde de titane et des nanoparticules de semi-conducteurs de nitrures, en particulier GaN/TiO2 et GaxIn1-xN/TiO2, (ii) de tester l’efficacité photocatalytique de ces matériaux sur plusieurs réactions photochimiques modèles (oxydation des thiols, trifluorométhylation, conversion des amines en imines), à la fois en réacteur fermé et en réacteurs photochimiques sous flux et (iii) d’étudier les options de changement d’échelle pour améliorer les taux de production de ces nanophotocatalyseurs.