Rémy Guillet-Nicolas

One-step-impregnation hard templating synthesis of high-surface-area nanostructured mixed metal oxides (NiFe2O4, CuFe2O4 and Cu/CeO2)

We report here on an efficient one-step-impregnation method to synthesize crystalline mesoporous bimetal oxides (e.g. NiFe(2)O(4), CuFe(2)O(4), Cu/CeO(2)) using mesoporous silicas as hard templates under optimized mixing conditions. This new procedure enables a true replication of the mesostructure with high yield and phase purity, while retaining particle morphology of the template.

pH-Responsive Nutraceutical–Mesoporous Silica Nanoconjugates with Enhanced Colloidal Stability†

An innovative platform for targeted oral drug delivery is proposed based on the functionalization of drug/dye-loaded mesoporous silica nanoparticles (MSNs) with a biodegradable nutraceutical (β-lactoglobulin). The attachment of the nutraceutical not only protects the drug/dye from leaching in acidic environment, but also effectively allows their release in desired basic sites (pH 7.4).

Luminescent triarylboron-functionalized zinc carboxylate metal-organic framework.

A luminescent triarylboron ligand functionalized with three carboxylic groups has been synthesized and fully characterized. Its use in boron-containing metal-organic frameworks (B-MOFs) has been demonstrated by the synthesis and isolation of a Zn(II)B-MOF compound (B-MOF-1). The crystals of B-MOF-1 belong to the cubic space group F432 with 8-fold interpenetrated networks and ∼21% void space. B-MOF-1 exhibits blue fluorescence and is capable of modest gas sorption of N(2), argon, and CO(2).

Tailor‐Made Mesoporous Ti‐SBA‐15 Catalysts for Oxidative Desulfurization of Refractory Aromatic Sulfur Compounds in Transport Fuel

We propose large‐pore titanium‐containing organosilylated mesoporous silica (Ti‐SBA‐15) as a highly efficient catalyst for the oxidative desulfurization (ODS) of refractory aromatic sulfur compounds with the aim to produce ultra‐low sulfur diesel. To achieve this, we synthesized a series of mesoporous Ti‐SBA‐15 catalysts according to a new procedure. The procedure is based on the controlled grafting of titanium chelates on SBA‐15 silica at low temperatures (5 °C). This specific synthesis procedure ensured a high dispersion of the required 4‐coordinate tetrahedral Ti4+ sites located on the mesopore surface. To substantiate the influence of the titanium content and mesopore size on the ODS performance of the catalysts, the parameters were varied in the range of 0.7 to 4.7 mol % (Si/Ti) and 5.1 to 9.0 nm, respectively. The resulting Ti‐SBA‐15 catalysts were then tested in the oxidative desulfurization (ODS) of model sulfur‐containing compounds in the presence of cumene hydroperoxide (CHP) as the organic oxidant. The ODS of a real industrial diesel fuel was also carried out in a continuous fixed bed reactor with the same Ti‐SBA‐15 catalysts and CHP. The catalytic results revealed that the Ti‐SBA‐15 catalysts with the largest pore sizes (>7.3 nm) and highest Ti contents (>2.8 mol %) were highly active catalysts for ODS reactions. Moreover, the catalysts with large pores and high Ti loadings appeared to be stable for over 30 h and were far less prone to deactivation than their equivalent Ti‐SBA‐15 samples with smaller pore diameters and lower Ti contents.

Substantiating the Influence of Pore Surface Functionalities on the Stability of Grubbs Catalyst in Mesoporous SBA‐15 Silica

The influence of pore surface functionalities in mesoporous SBA-15 silica on the stability of a model olefin metathesis catalyst, namely Grubbs I, is substantiated. In particular, it is demonstrated that the nature of the interaction between the ruthenium complex and the surface is strongly depending on the presence of surface silanols. For this study, differently functionalized mesoporous SBA-15 silica materials were synthesized according to standard procedures and, subsequently, the Grubbs I catalyst was incorporated into these different host materials. All of the materials were thoroughly characterized by elemental analyses, nitrogen physisorption at -196 °C, thermogravimetric analyses, solid-state NMR spectroscopy, and infrared spectroscopy (ATR-IR). By such in-depth characterization of the materials, it became possible to achieve models for the surface/catalyst interactions as a function of surface functionalities in SBA-15; for example, in the case of purely siliceous silanol-rich SBA-15, octenyl-silane modified SBA-15, and silylated equivalents. It was evidenced that large portions of the chemisorbed species that are detected spectroscopically arise from interactions between the tricyclohexylphosphine and the surface silanols. A catalytic study using diethyldiallylmalonate in presence of the various functionalized silicas shows that the presence of surface silanols significantly decreases the longevity of the ring-closing metathesis catalyst, whereas the passivation of the surface by trimethylsilyl groups slows down the catalysis rate, but does not affect significantly the lifetime of the catalyst. This contribution thus provides new insights into the functionalization of SBA-15 materials and the role of surface interactions for the grafting of organometallic complexes.

Insights into pore surface modification of mesoporous polymer-silica composites: introduction of reactive amines

Pore surface engineering of mesoporous materials is fundamental for the development of highly selective sorbents, solid catalysts or drug delivery systems. In the present study, tailored mesoporous amine-functionalized polymer–silica composites are synthesized using a two-step mesopore surface-confined polymerization technique. For this, a functional polymer, polychloromethylstyrene (PCMS), is first introduced as a uniform coating on the mesopore surface of mesoscopically ordered silica, e.g. SBA-15 or KIT-6 materials. In the second step, selected amines, as model functions, are attached to the polymer surface by nucleophilic substitution, generating a variety of nanoporous amino-polymer–silica composites. In particular, it is shown that this approach allows for a tuning of surface concentration of the organic groups either by varying polymer loading or by copolymerization of the CMS monomers with non-reactive monomers (styrene). Moreover, this method is suitable for facile introduction of diverse types of amine groups, e.g. secondary amines, diamines, linear or branched polyamines. The pristine mesoporous silica hosts and the different functional mesoporous polymer–silica composites are characterized in detail by nitrogen physisorption, powder X-ray diffraction, elemental analysis, thermogravimetry–differential thermal analysis coupled with mass spectrometry (TG-DTA/MS), attenuated total reflection-IR spectroscopy (ATR-IR) and scanning electron microscopy. In addition, the obtained functionalized mesoporous composites are proven active as base catalysts in the Knoevenagel condensation. From these investigations, it appeared that the preparation method should be highly flexible and appropriate to enable modulation of location and distribution of various functional groups within mesopores.

Insights into the pore structure of KIT-6 and SBA-15 ordered mesoporous silica – recent advances by combining physical adsorption with mercury porosimetry

We have performed a systematic study of N2 adsorption at 77 K and Hg porosimetry experiments at 298 K on highly ordered KIT-6 and SBA-15 silicas exhibiting noticeably different pore structures with pore diameters in the 7–11 nm range. Accurate pore structure analysis was performed by applying appropriate NLDFT methods to the N2 physisorption data. Mercury intrusion/extrusion experiments on KIT-6 silicas (up to 415 000 kPa) showed no collapse of the pore structure quite remarkably. To the best of our knowledge, this is the first successful example of Hg porosimetry on KIT-6 materials. Hence, it was possible to utilize KIT-6 mesoporous molecular sieves for quantitatively testing the validity of the Washburn equation applied to mercury intrusion for pore size analysis. KIT-6 silicas also allowed investigating the analogies between condensation/evaporation mechanisms of wetting (N2 at 77 K) and non-wetting (Hg at 298 K) fluids as a function of the pore size confirming the thermodynamic consistency between Hg intrusion/extrusion and capillary evaporation/condensation. Contrary to KIT-6 silicas, Hg porosimetry experiments on SBA-15 materials of identical pore diameters show an inconsistent behavior in a sense that both reversible Hg intrusion/extrusion data and partial collapse of the pore structure were observed. Our work clearly demonstrates that combining advanced physical adsorption and Hg porosimetry studies provides a more thorough understanding of textural features and shed some light on the fundamental questions concerning the effect of confinement on the phase behavior of wetting and non-wetting fluids.

Identification of the Basic Sites on Nitrogen-Substituted Microporous and Mesoporous Silicate Frameworks Using CO2 as a Probe Molecule

Carbon dioxide was shown to identify surface basic properties of nitrogen-substituted microporous and mesoporous silicas, in addition to conventional basic oxides, by a detailed study using isotherm and heat of adsorption measurements as well as by infrared spectroscopy. A hydrogen-bonded weak interaction was primarily observed between CO2 and silanol (Si-OH) and silamine (Si-NH-Si) groups. The heat of adsorption of CO2 demonstrated that the latter adspecies were formed preferentially over the former, although a much higher amount of linear CO2 adspecies were found on SBA-15 mesoporous silica because of the presence of a large quantity of silanol groups on its surface. Carbamate-type chemisorbed adspecies were not detected on silamino sites, whereas carbonate-type adspecies were formed on alkali ion-exchanged zeolites and also residual sodium ions on the surface of silicalite-1. CO2 was shown to be a successful probe molecule for identifying weakly interactive hydrogen-bonding sites, and it has potential as a surface probe for strongly interactive nucleophilic sites derived from alkaline ions or a methylated silamino group, Si-N(CH3)-Si.