Water-Stable, Nonsiliceous Hybrid Materials with Tunable Porosity and Functionality: Bridged Titania-Bisphosphonates

Combining the properties of organic and inorganic moieties with high surface areas and pore volumes offers endless possibilities to design materials adapted to a wide range of advanced applications. The vast majority of mesoporous hybrid materials are siliceous materials, and developing low-cost synthetic methodologies leading to water stable nonsiliceous hybrid materials with controlled texture and functionality is essential. We report here an original strategy for the synthesis of mesoporous bridged titania-bisphosphonate hybrids based on a one-step, templateless nonhydrolytic sol–gel route. The reaction of Ti­(OiPr)4 and a rigid bisphosphonate ester in the presence of Ac2O leads to the formation of TiO2 anatase nanorods cross-linked by fully condensed bisphosphonate groups. The porosity can be readily adjusted over a wide range by changing the reaction conditions, and very high specific surface areas (up to 720 m2 g–1) and pore volumes (up to 1.85 cm3 g–1) can be reached. The texture is stable in aqueous media between pH 1 and pH 12. Furthermore, accessible functional organic groups can be easily incorporated using either functional bisphosphonates or easily available monophosphonate compounds. The accessibility of bipyridyl organic groups was checked by Cu2+ adsorption from aqueous solutions. The unique combination of texture, functionality, and stability displayed by bridged titania-bisphosphonates makes these promising materials complementary of other hybrid materials such as organosilicas, MOFs, or mesoporous metal phosphonates

One-Step Synthesis of Mesoporous Hybrid Titania−Silica Xerogels for the Epoxidation of Alkenes

One-Step Synthesis of Mesoporous Hybrid Titania−Silica Xerogels for the Epoxidation of Alkene

Surfactant-Free Organo-Soluble Silica−Titania and Silica Nanoparticles

Surfactant-Free Organo-Soluble Silica−Titania and Silica Nanoparticle

Improvement of the Oxidative Stability of Nanodiamonds by Surface Phosphorylation

Surface phosphorylation of nanodiamond was performed by reaction with phosphoryl chloride in dichloromethane. Depending on the reaction conditions, P contents of up to 1.66 mmol/g were reached. Phosphorylation dramatically enhanced the thermal stability of nanodiamond under oxidizing conditions, shifting the oxidation temperature by up to 190 °C and dividing the oxidation rate by a factor of up to 160. The nature of the grafted phosphate species and their evolution during thermal treatment was followed using solid-state NMR

Surface Functionalization of Detonation Nanodiamonds by Phosphonic Dichloride Derivatives

A new method for the functionalization of detonation nanodiamonds (DNDs) is proposed, on the basis of surface modification with phosphonic dichloride derivatives. DNDs were first modified by phenylphosphonic dichloride, and the grafting modes and hydrolytic stability under neutral conditions were investigated using ¹H, ¹³C, and ³¹P solid state NMR spectroscopy, Fourier transform infrared spectroscopy, as well as elemental analysis. Then, in order to illustrate the possibilities offered by this method, DNDs functionalized by mesityl imidazolium groups were obtained by postmodification of DNDs modified by 12-bromododecylphosphonic dichloride. The oxidative thermal stability of the functionalized DNDs was investigated using thermogravimetric analysis

Interlayer surface modification of the protonated ion-exchangeable layered perovskite HLaNb₂O₇•<i>x</i>H₂O with organophosphonic acids

The interlayer surface of a protonated form of the Dion−Jacobson-type ion-exchangeable layered perovskite, HLaNb2O7·xH2O (HLaNb), has been successfully modified with various organophosphonic acids [phenylphosphonic acid (PhPO(OH)2, PPA) and n-alkylphosphonic acids (n-CnH2n+1PO(OH)2 with n = 4−18, APAs)] to produce graft-type organic derivatives using an n-decoxy derivative of HLaNb (C10O-HLaNb) as an intermediate. The interlayer distances of the products are changed from that of the intermediate, 2.73 nm, to 2.31 (PPA/C10O-HLaNb) and 2.31−5.26 (APAs/C10O-HLaNb) nm. IR and solid-state 13C CP/MAS NMR spectra of the products reveal that n-decoxy groups are removed and phenyl (PPA/C10O-HLaNb) or n-alkyl groups (APA/C10O-HLaNb) are introduced. Elemental analysis reveals that the amounts of PPA- and APA-moieties are 0.88−0.99 per [LaNb2O7], corresponding approximately to the amount of the n-decoxy groups in C10O-HLaNb. The environment of interlayer species in PPA/C10O-HLaNb is assumed to be monodentate PhPO(OH)(ONb) based on the IR results (the P−O stretching and P−OH stretching bands at ∼1030 and ∼950 cm−1) and the reaction between PPA/C10O-HLaNb and n-butylamine (−NH2/POH = 1.0). Scanning electron micrographs of the products reveal that the morphology is clearly preserved during the reactions with PPA or APAs, indicating that they are graft-type rather than dissolution−recrystallization-type reactions. Because water is required for the reaction between PPA and C10O-HLaNb, this reaction is assumed to proceed via the formation of an (HO)NbO5 site and its subsequent reaction with PPA. A linear relationship is clearly observed between the number of carbon atoms in the n-alkyl chains and the interlayer distances of APAs/C10O-HLaNb, and a structural model of APAs/C10O-HLaNb with a n-alkyl chain tilt angle of 57° is proposed

Syntheses, Characterizations, and Single-Crystal X-ray Structures of Soluble Titanium Alkoxide Phosphonates

Reactions of Ti(OiPr)4 with different phosphonic acids RPO3H2 (R = Ph, 4-CNPh, Me, tBu) in organic solvents have been investigated. In the presence of small amounts of water, the new molecular titanium oxide alkoxide phosphonates [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(RPO3)3]·DMSO [R = Ph (1), Me (2), tBu (3), 4-CNPh (4)] were isolated. The single-crystal X-ray structure analyses of 1 and 2 revealed hexacoordinated titanium atoms and a connectivity of (111) for each phosphonate. Under rigorous exclusion of water, the reaction of Ti(OiPr)4 with tert-butylphosphonic acid in toluene gave the titanium phosphonate tetramer [Ti(OiPr)2(tBuPO3)]4 (5). A single-crystal X-ray structure analysis of 5 revealed a 5 + 1 coordination of the titanium atoms as a result of the (112) connectivity of each phosphonate; such a coordination mode has never been reported for a titanium phosphate, phosphonate, or phosphinate. Compounds 1−5 were characterized by FT-IR, 31P MAS NMR, and solution multinuclear NMR (1H, 13C{1H}, 31P{1H}) spectroscopies. 13C CP MAS NMR experiments were carried out on arylphosphonates 1 and 4. Solution NMR experiments were also used to investigate the exchange reaction between 1 and 2 and the conversion of 5 to [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(tBuPO3)3]·iPrOH by partial hydrolysis in the presence of Ti(OiPr)4. The phosphonate clusters 1−5 are soluble in organic solvents and are likely intermediates in the sol−gel processing of inorganic−organic hybrids based on titanium oxide and phosphonate groups that we are currently developing

High-Field ¹⁷O MAS NMR Investigation of Phosphonic Acid Monolayers on Titania

High-field 17O MAS NMR was used to investigate the binding of self-assembled monolayers of 17O-enriched phosphonic acids deposited on a titania anatase support. The spectra were recorded at two different magnetic fields (9.4 and 17.6 T), to improve the reliability of the simulations of the different resonances. The spectra recorded at 17.6 T offer an excellent resolution between the different oxygen sites, PO, P−O−H, and P−O−Ti, thus greatly facilitating their quantification. The data reported here give direct evidence of the extensive formation of Ti−O−P bonds in the surface modification of titania by phosphonic acids. The presence of residual PO and P−O−H sites indicates the presence of several different binding modes in phosphonic acid monolayers. The chemical shift of P−O−Ti sites is consistent with bridging (as opposed to chelating) modes

A one step non-hydrolytic sol-gel route to mesoporous Re- and Mo-based mixed oxides for olefin metathesis

<p>The simplicity of NHSG makes it attractive: multi-step procedures, expensive precursors, or reactivity modifiers are not needed.</p> <p>Poster presented at the Europacat conference September 2, 2013, Lyon, France.</p

Design of SiO₂−Al₂O₃−MoO₃ Metathesis Catalysts by Nonhydrolytic Sol−Gel

MoO3-based heterogeneous catalysts prepared by dispersion of Mo-oxide species on preformed supports are highly regarded candidates for industrial light olefin metathesis. An original approach for the elaboration of Mo-based catalysts is presented here. Mesoporous ternary Si/Al/Mo mixed oxides are prepared in one step by a nonhydrolytic sol−gel route in nonaqueous medium. Taking advantage of the migration of Mo species during the calcination, effective catalysts with very good textures and highly dispersed surface Mo species are obtained, as shown by XRD, XPS, and TOF-SIMS characterization. The presence of isolated Mo species is evidenced and these species are proposed to be the precursors to the active species in the metathesis of propene. These new materials compare well with catalysts prepared by classical wet impregnation of silica−alumina supports with ammonium heptamolybdate, eventually outperforming them at high Mo loading