Hexagonal Mesoporous Silica Materials Research Articles

The use of inorganic Al-HMS as a support for NiMoW sulfide HDS catalysts

Inorganic hexagonal mesoporous silica (HMS) and aluminum modified HMS materials (Al-HMS) were prepared and used as supports of transition metal sulfide hydrodesulfurization (HDS) catalysts based on nickel, molybdenum, and tungsten as active phase. The samples were characterized with XRD, HRTEM, TPD, N2 physisorption and UV–Vis. The catalytic activity of the trimetallic catalysts was performed in the HDS of dibenzothiophene (DBT). When Al was incorporated into the inorganic support, important changes and effects were observed on the physicochemical properties. On the other hand, the incorporation of Al into the HMS led to a decrease in the reaction rate (k) and a trend toward a direct path of desulfurization was observed for all materials.

A DRIFTS study of moisture adsorption on hexagonal mesoporous (HMS) silica supported composites

Hexagonal Mesoporous Silica (HMS) materials supported composite materials were synthesized to remove trace moisture in the gas insulated switchgear (GIS) in this work. And an infrared study has been performed on the adsorption-desorption process of water vapor on these composites before and after polyethyleneimine (PEI) loading. It was found that the amino groups of PEI at high loading amounts functioned as the main active sites for H2O capture. These adsorbed water clusters tended to associate with composite materials through weak hydrogen-bonding interactions and could be easily regenerated under nitrogen flow. The three-dimensionally interconnected pores of HMS and the maintained alkylamine surfactants facilitated the dispersion of loaded PEI, improving the diffusion and adsorption properties of moisture. The results herein implied that PEI/HMS composites would be a kind of appealing materials for moisture capture in GIS due to its superior moisture adsorption capacity and excellent cyclic performance.

Highly ordered and hexagonal mesoporous silica materials with large specific surface from natural rectorite mineral

Highly ordered and hexagonal mesoporous silica materials containing aluminum were successfully synthesized from natural rectorite mineral via a novel strategy. Silicon and aluminum sources were obtained from rectorite mineral by a pretreatment method involving acid leaching, alkali leaching and strongly acidic cation exchange resins (SACERs) treating, followed by a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as template and subsequent calcination to prepare Al-MCM-41. More importantly, Wide angle X-ray diffraction (WAXRD), fourier transform infrared spectroscopy (FT-IR) and solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated that acid treatment did not destroy the structure of natural rectorite. Unlike other silicate minerals, natural rectorite failed to provide suitable silicon sources because of residual hydroxide from alkali leaching process. In this paper, SACERs instead of inorganic acids were adopted to neutralize residual hydroxide, which avoided excessive inorganic anions to hinder the synthesis of Al-MCM-41 by a hydrothermal reaction. The final Al-MCM-41 products were amorphous SiO2, with a surface area of 1032 m2/g, pore volume of 0.97 cm3/g and an average pore diameter of 2.6 nm. A proposed mechanism for synthesizing mesoporous silica from natural rectorite was suggested.

Catalytic Ethylene Oligomerization over Ni/Al-HMS: A Key Step in Conversion of Bio-Ethanol to Higher Olefins

Al-modified hexagonal mesoporous silica (HMS) materials were synthesized using dodecylamine as a template according to the methods reported in the literature. FT-IR spectra proved that Al3+ ions entered in the HMS framework in Al-HMS (prepared by sol-gel reaction) but Al3+ ions existed in the extra-framework in Al/HMS (prepared by post-modification). NH3-TPD indicated that either Al-HMS or Al/HMS had solid acid sites on the surface, and the acidic strength of Al/HMS was stronger than that of Al-HMS. For ethylene oligomerization at 200 °C under 1 MPa, Ni/Al-HMS showed an ethylene conversion of 96.3%, which was much higher than that over Ni/Al/HMS (45.6%). The selectivity for C4H8, C6H12, C8H16, and C8+ was 37.7%, 24.5%, 24.0%, and 9.1% for ethylene oligomerization over Ni/Al-HMS, respectively. Ni/Al-MCM-41, which has been reported as an effective catalyst for ethylene oligomerization in the literature, showed a high ethylene conversion (95.2%) similar to that of Ni/Al-HMS in this study. However, the selectivity for C8H16 over Ni/Al-MCM-41 (16.3%) was lower than that over Ni/Al-HMS (24.0%) in the ethylene oligomerization. For ethanol dehydration at 300 °C under 1 MPa, a commercial H-ZSM-5 catalyst showed a high ethylene yield (91.2%) after reaction for 24 h using a feed containing 90 wt.% ethanol and 10 wt.% water. In this study, a two-step process containing two fixed-bed reactors and one cold trap was designed to achieve the direct synthesis of higher olefins from bio-ethanol. The cold trap was used to collect the water formed from ethanol dehydration. By using H-ZSM-5 as a catalyst for ethanol dehydration in the first reactor and using Ni/Al-HMS as a catalyst for ethylene oligomerization in the second reactor, higher olefins were continuously formed by feeding a mixture containing 90 wt.% ethanol and 10 wt.% water. The yields of higher olefins did not decrease after reaction for 8 h in the two-step reaction system.

Dodecylamine Template-Based Hexagonal Mesoporous Silica (HMS) as a Carrier for Improved Oral Delivery of Fenofibrate.

The aim of present investigation was the preparation of dodecylamine template-based hexagonal mesoporous silica (HMS) as a carrier for poorly water-soluble drug (fenofibrate). HMS material has distinctive characteristics such as easy synthesis, high surface area and wormhole pores. These characteristics are highly admirable to make use of it as a carrier in drug delivery system. HMS was prepared by pH and temperature-independent process. Fenofibrate was loaded into the HMS by solvent immersion method using organic solvent. The BET surface area of HMS was evaluated by nitrogen adsorption/desorption analysis. HMS and drug-loaded HMS were characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and contact angle study. The HMS-based system was also evaluated for in vitro and in vivo study as compared to plain drug. The BET surface area of HMS was found 974m2/g with a narrow pore size average of 2.6nm. The DSC and XRD study confirmed the amorphization of drug within the HMS. SEM and TEM study showed morphological features of HMS as well as revealed the wormhole porous structure. Contact angle study showed improvement in aqueous wetting property of drug within the HMS (contact angle 46°). The In vitro drug release study showed a remarkable dissolution enhancement in HMS-based system as compared to plain drug. In vivo pharmacodynamic study (hyperlipidaemia model) exhibited HMS-based formulation was significantly improved the bioavailability of fenofibrate. Thus, HMS has admirable properties; makes it a potential carrier for delivery system of poorly water-soluble drugs.

Investigation of Hexagonal Mesoporous Silica-Supported Composites for Trace Moisture Adsorption.

Moisture control is an important part of effective maintenance program for gas-insulated switchgear (GIS). Herein, hexagonal mesoporous silica (HMS) materials were synthesized by adopting dodecylamine as a structure directing agent, which was then employed as a host for supporting polyethylenimine (PEI) without further calcinations or extraction treatment. The physicochemical properties of the silica support and composites were characterized, and the moisture adsorption capacity of these composites was determined. The reserved template agents resulted in a dramatic improvement in moisture adsorption amount. Among them, 50PEI/DHMS showed the highest adsorption value. The enhanced adsorption could be attributed to the generated hydrogen bonding between amino groups and H2O molecules and the improved diffusion of moisture into the bulk networks of PEI polymers due to its better spatial dispersion imposed by the long alkyl chains of template agents, which was confirmed by thermogravimetry results and hydrogen efficiency analysis. Moreover, the maintained terminal amino groups of templates could also function as active sites for moisture adsorption. The results herein imply that the PEI/DHMS composites could be appealing materials for capturing moisture in GIS.

Metal-enhanced fluorescence effect of Ag and Au nanoparticles modified with rhodamine derivative in detecting Hg2+

In this study, two metal-enhanced fluorescence chemosensors, metal mesoporous materials (hexagonal mesoporous silica (HMS) material loading with Ag and Au NPs were defined as Ag-HMS and Au-HMS) functionalized by rhodamine derivative R, have been prepared by a simple and effective impregnation–reduction method and used for Hg2+ detection in aqueous media. These materials were characterized by transmission electron microscopy (TEM), N2 physical adsorption–desorption, X-ray powder diffraction (XRD), UV–Vis spectrum and Fourier transform infrared spectroscopy (FT-IR). Both HMS-Ag-R and HMS-Au-R chemosensors have high selectivity toward Hg2+ in presence of interfering ions. According to the results, the suitable content of Ag and Au NPs is 2 wt% in the metal nanocomposite Ag-HMS and Au-HMS, respectively. In this paper, HMS-Ag-R shows a higher enhancement factor (EF) of 4.58 comparing with HMS-Au-R (EF = 2.93) in presence of 100 ppb Hg2+. The detection limits of HMS-Ag-R and HMS-Au-R for Hg2+ were determined as 0.9 and 1.4 ppb, respectively. Furthermore, the fluorescence lifetime of R reduced slightly after introducing Ag and Au NPs, and the localized surface plasmon resonance spectra of Ag and Au NPs all exhibited blueshift after immobiling rhodamine derivative R. It can be concluded that the metal-enhanced fluorescence effect of Ag-HMS is more powerful than Au-HMS.

A metal-enhanced fluorescence sensing platform based on new mercapto rhodamine derivatives for reversible Hg2+ detection

A new metal-enhanced fluorescence (MEF) chemosensor HMS-Ag-R-2SH for Hg2+ has been prepared via a simple and effective method. The fluorescent chemosensor was based on a mercapto rhodamine derivatives linked with Ag nanoparticles, and the Ag nanoparticles were supported on hexagonal mesoporous silica material (HMS). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), absorption spectroscopy and fluorescence spectroscopy techniques were employed to characterize morphology, mesostructure and spectral features of the chemosensor. This chemosensor works in a nearly pure aqueous solution with a broad pH range. The output signals include color change and fluorescence. Moreover, HMS-Ag-R-2SH presents excellent anti-disturbance ability when exposed to a series of competitive cations such as Ag+, K+, Li+, Na+, Ba2+, Ca2+, Cd2+, Co2+, Cu2+, Mg2+, Mn2+, Ni2+, Pb2+, Zn2+, Al3+, Cr3+ and Fe3+. The selectivity of this chemosensor was significantly improved due to the introduction of the sulphydryl. The chemosensor showed a lower detection limit of 2.1ppb for Hg2+. Importantly, HMS-Ag-R-2SH could be regenerated with sodium sulfide solution for several cycles and maintain a high sensitivity.

High‐Temperature Synthesis of Ordered Hexagonal Mesoporous Silica Materials (SBA‐15) with Adjustable Large Mesopores for Selective Adsorption of Biomolecules

AbstractAL‐SBA‐15 materials with additional large‐mesopore networks have been successfully synthesized at high‐temperature (200 °C) in the presence of inorganic salts. Compared with conventional SBA‐15 which has monomesopores, the samples synthesized by using cations and assisted by high‐temperature show a bimodal pore size distribution. Interestingly, the large mesopores in the samples can be tuned by a simple adjustment in the preparation time and temperature. In addition, this route also results in the formation of a high degree of silica condensation which is favorable for improvement of sample hydrothermal stability. More importantly, the adsorption and separation of biomolecules over AL‐SBA‐15 materials and conventional SBA‐15100 or SBA‐15200 samples shows that AL‐SBA‐15 samples exhibit superior selective adsorption and separation capabilities compared with conventional samples and this is potentially important for their applications in adsorption and separation of bulky biomolecules.

Hydrophobic bifunctionalized hexagonal mesoporous silicas as efficient adsorbents for the removal of Orange IV

A novel hydrophobic bifunctionalized hexagonal mesoporous silica (Ph-Am-HMS) material was synthesized with the simultaneous immobilization of phenyl and amino groups on its surface. The composition and structure of Ph-Am-HMS were studied by FT-IR, XRD, N2 adsorption–desorption, and sessile water droplet contact angle measurements, etc., which revealed that this novel bifunctionalized material showed hydrophobicity and good porous properties. When applied to the adsorption of the azo dye Orange IV in aqueous solutions, Ph-Am-HMS exhibited a high adsorption capacity and a rapid adsorption rate. The theoretical maximum adsorption capacity could reach 246.3 mg g−1 in 60 min at 293 K. A kinetic study indicated that the adsorption of Orange IV on Ph-Am-HMS fitted perfectly to the Freundlich adsorption model and followed pseudo-second-order kinetics. The changes in Gibbs free energy (−10.55 kJ mol−1), enthalpy (−7.06 kJ mol−1), and entropy (11.83 J mol−1 K−1) at 293 K showed that the adsorption process was spontaneous and exothermic.

Modified supercritical CO2 extraction of amine template from hexagonal mesoporous silica (HMS) materials: Effects of template identity and matrix Al/Si molar ratio

In this work, the primary amine template has been extracted from freshly synthesized hexagonal mesoporous silica (HMS) materials by means of modified supercritical carbon dioxide at 60–85°C under 10.0–20.0MPa. The influences of amine identity and matrix Al/Si ratio on the extraction efficiencies and structural properties of HMS thus obtained are investigated in detail. The results show that the extraction efficiency is strongly dependent on the pore size of the HMS materials produced by five different templates. For aluminium-incorporated samples, the extraction efficiency is observed to decrease with the Al/Si molar ratio since as the Al/Si molar ratio increases, more amine will get protonated and the matrix/template interactions become stronger, subsequently rendering the extraction more difficult and the efficiency decrease. The formic acid modifier has resulted in better extraction performance than methanol, yielding higher extraction efficiencies. The SFE-treated materials exhibit better structural properties like higher pore volume and specific surface area as compared to those prepared by conventional calcinations. Besides, results of pyridine adsorption and conversion of 2-propanol to propylene suggest that the SFE-treated HMS materials may have higher acidity than the directly calcined samples.

Organo-functionalized mesoporous silicas for efficient uranium extraction

A series of new mesoporous silica (MS) sorbents were developed by functionalizing a large-pore 2-D hexagonal MS material, MSU-H, with amidoxime, imide dioxime, phosphonate, and carboxylate functional groups, and characterized by nitrogen adsorption, ζ-potential, infrared spectroscopy, and thermogravimetric analysis. These MS materials have a grafting density of 0.75 to 1.38mmol/g, and exhibit BET surface areas of 186–526m2/g and average pore sizes of 3.8–7.8nm. The uranyl sorption by the functionalized MS sorbents was investigated in basic water and artificial seawater at pH=8.3±0.1. The MS materials exhibited a high U sorption capacity in water (>40μgU/mg sorbent) with Langmuir isotherms suggesting a saturation U sorption capacity of 185.2μgU/mg sorbent for the phosphonic acid-modified MS material (MSPh-III). The U sorption capacity in artificial seawater was reduced to 12.1μgU/mg sorbent for MSPh-III. Langmuir isotherms indicated a saturation sorption capacity of 66.7μgU/mg sorbent for MSPh-III, which also had the greatest binding affinity for U of all sorbents tested, followed by the imide dioxime-functionalized material MSCA-I. Kinetics studies show rapid uranyl sorption and equilibration in less than 40min. The U was quantitatively eluted from the MS sorbents by washing with strong acid (>0.1M HCl). This work represents the first comprehensive study of organo-functionalized MS materials for U extraction, and shows that phosphonic acid- and imide dioxime-functionalized MS materials provide excellent platforms for developing novel sorbents for efficient U extraction from seawater.

Time-Dependent Protein Adsorptive Behavior on/in Mesoporous Silica Materials

The Time – Dependent Adsorptive Behavior of Biomolecules on/in Mesoporous Silica Materials (MPS) Have Been Studied by Using Transmission Electron Microscopy (TEM). Highly Ordered Hexagonal Mesoporous Silica Materials (SBA-15) Synthesized Were Immersed in Phosphate Buffer Saline (PBS) Solution Containing Cytochrome C for 2, 48, and 120 Hours at 4 °C. after that, MPS Materials Were Rinsed with PBS Solution, and then Immersed in PBS Solution without Cytochrome C. the Amount of Protein Adsorbed on/in MPS Materials Soaked for 2, 48, and 120 Hours Was 75 Mg/g, 135 Mg/g and 178 Mg/g, Respectively. the Time Profiles for Adsorption of Proteins Can Be Well Described by Intraparticle Diffusion Model. the Holes of MPS Materials Were Observed to Be Overlapped with Stained Proteins for First 2 Hours Immersion. the Stained Proteins Were Observed between Primary Particles and Partly inside the Mesoporous Channels in the MPS Material Immersed for 48 Hours. for MPS Immersed for 120 Hours, Stained Proteins Were Observed in Almost All Meso-Scale Channels of MPS. the Ratio of Desorbed Proteins from those Embedded on/in MPS Materials Was 13 % in Case of the MPS Materials Immersed in PBS Containing Cytochrome C for 2 Hours, while 8 % in Case of the MPS Materials Immersed for 48 and 120 Hours. Cytochrome C May Be Strongly Embedded on/in MPS Materials due to the Electrostatic Effect.

Structural Investigation of Nonionic Fluorinated Micelles by SANS in Relation to Mesoporous Silica Materials

In an attempt to answer the question if there is dependence between the pore ordering of the mesoporous silica, obtained through the cooperative template mechanism, and the shape of the micellar aggregates of the surfactant solutions, the micellar structures of two nonionic fluorinated surfactant based-systems are studied by SANS. By fitting the experimental spectra with theoretical models, the structural evolution of the molecular aggregates can be described, and some important parameters can be obtained, such as the water and eventually oil penetration into the surfactant film, the aggregation number, the area per polar head of the surfactant, and the surfactant chain conformations. We have shown that for the C(8)F(17)C(2)H(4)(OC(2)H(4))(9)OH system, the micelles are prolate spheroids. The increase of the surfactant concentration in water does not change the characteristics of the interfacial film, but the aggregation number raises and the particles become more elongated. By contrast, the experimental curves of C(7)F(15)C(2)H(4)(OC(2)H(4))(8)OH cannot be fitted considering a small particle model. However, progressive incorporation of fluorocarbon induces a change of size and shape of the globules, which become smaller and more and more spherical. Regarding the material mesopore ordering, it appears that the micelles that lead to hexagonal mesoporous silica materials are described with a model of quasi-spherical globules. On the contrary, when large micelles are found, only wormhole-like structures are obtained.

Organic template removal from hexagonal mesoporous silica by means of methanol-enhanced CO 2 extraction: Effect of temperature, pressure and flow rate

Supercritical fluid extraction was evaluated for removing the amine surfactant from hexagonal mesoporous silica materials. In this study, methanol-enhanced supercritical CO 2 extraction was carried out on freshly synthesized materials by means of a dynamic method. Experiments were performed at pressure ranging from 10.0 to 25.0 MPa, temperature from 45 to 105 °C, CO 2 flow rate from 0.45 to 4.5 ml/min, and methanol flow rate from 0.05 to 0.5 ml/min. The influence of these parameters on the extraction has been evaluated in terms of the surfactant recovery. The results show that by using this method up to 96% of the total amine surfactant used is extracted out of as-synthesized mesoporous materials within 1 h extraction whereas only 78% of the surfactant can be removed by liquid ethanol extraction. The materials processed by supercritical CO 2 extraction are found to possess better structural properties as reflected by the X-ray diffraction analysis and N 2 adsorption results, and thus have higher thermal and hydrothermal stability than those obtained by liquid ethanol extraction or high temperature calcination.

Amine extraction from hexagonal mesoporous silica materials by means of methanol-enhanced supercritical CO2: Experimental and modeling

In this work, dodecylamine was extracted from freshly synthesized hexagonal mesoporous silica materials under pressure of 15.0–25.0MPa and temperature of 50–105°C with methanol-enhanced supercritical carbon dioxide. The effects of pressure, temperature, and solvent flow rate on the amine extraction recovery were studied. The experimental results show over 95% of the total amine used was extracted within 1h at 25.0MPa and 85°C, and that the extraction recovery increased with pressure, supercritical solvent flow rate or methanol flow rate. The extraction data were described by an empirical model, a hot ball Crank model and a diffusion-layer theory model and the relative merits of the models were demonstrated. The calculations were compared with those experimentally obtained. Very nice agreement between the diffusion-layer theory model and our experimental measurements was achieved as reflected by the average absolute relative deviation being less than 6.0%. The empirical and hot ball Crank models both gave relatively poorer fit than the diffusion-layer theory model.

Ordered hexagonal mesoporous silica materials (SBA-15) with additional disordered large-mesopore networks formed by gaseous expansion

Ordered hexagonal mesoporous silica materials with additional disordered large-mesopore networks (DL-SBA-15s) have been prepared by one-pot process using urea as a producer of gas. Combined characterizations of XRD, SEM, and TEM techniques show that DL-SBA-15s not only have ordered 2D hexagonal mesopores (about 10 nm) similar to SBA-15, but also have another disordered large-mesopore network (about 20 nm) interconnected with hexagonal mesoporous channels, which are confirmed by nitrogen isotherms. The ordered hexagonal mesopores are templated by polymer surfactant micelle, and disordered large-mesopores are formed by gaseous expansion due to the decomposition of urea added in the silica gel. 29Si MAS NMR and FT-IR spectra show DL-SBA-15s have high degree of silica condensation and low silanols on the surface, compared with SBA-15. Furthermore, we have compared the adsorption capacity of myoglobin over conventional SBA-15 and DL-SBA-15 samples, and the results show that DL-SBA-15s exhibit much higher adsorption rate than conventional SBA-15 due to the presence of additional disordered large-mesopore networks and larger pore volume, which is potentially important for immobilization of enzymes on ordered mesoporous materials.

Gelatin-assisted porous expansion of mesoporous silica

In this study, we report the pore expansion effect of gelatin, a common amphoteric biological protein, on the hexagonal mesoporous silica materials. Tetraethyl orthosilicate (TEOS) was used as silica source and the nonionic surfactant P123 (EO20PO70EO20) as template. The microstructure characters of products were investigated by low-angle X-ray diffraction (LAXRD), transmission electron microscope (TEM), and N2 adsorption–desorption measurements. The results show that the products prepared with gelatin have the mild expansion ratios of 29–39% and 5–22% in pore diameter and pore volume, respectively. The specific surface area of products ranges from 445 to 590 m2 g−1. Moreover, it is revealed that the presence of gelatin did not change the intact 2D-hexagonal mesoporous structure of materials. The ultraviolet–visible absorption spectroscopy (UV–Vis) analysis indicates that there is an interaction between the oxygen atoms of P123 and gelatin molecules. The pore expansion may be because the gelatin can interact with the hydrophilic sides of P123 micelles via hydrogen bonds interaction, which is different from the reported pore expansion mechanisms for other systems.

Carbon dioxide capture using amine-impregnated HMS having textural mesoporosity

A series of HMS (hexagonal mesoporous silica) materials having different textural mesoporosities was synthesized using dodecylamine as a structure directing agent, which were employed as a host for supporting PEI (polyethylenimine) (PEI/HMS) as a CO 2 capturing agent. The textural properties of the prepared materials were examined by XRD, N 2 adsorption–desorption isotherms, and SEM. CO 2 sorption/desorption measurements were carried out using a TGA unit using high purity (99.999%) CO 2. The as-prepared HMS alone exhibited a moderate sorption capacity of 34 m g C O 2 /g sorbent at 25 °C. The PEI/HMS prepared using a HMS having complementary textural mesopores exhibited CO 2 sorption capacity of 128 m g C O 2 /g sorbent with a 45 wt% PEI loading at 75 °C, whereas a sorption capacity of 94 m g C O 2 /g sorbent only was obtained under the same loading level using a HMS host with negligible textural mesoporosity. In addition, we were able to increase the PEI loading to 60 wt% without losing the capturing efficiency of the former, and achieved a CO 2 sorption capacity of 184 m g C O 2 /g sorbent, one of the highest capturing capacities reported in the literature thus far under the given conditions. PEI/HMS exhibited only a minor drop in CO 2 capture capacity during a 4 repeated cyclic sorption–desorption run at 75 °C.

Grafting of vanadyl acetylacetonate onto organo-hexagonal mesoporous silica and catalytic activity in the allylic epoxidation of geraniol

Vanadyl(IV) acetylacetonate ([VO(acac) 2]) was grafted onto a hexagonal mesoporous silica (HMS) using three different methodologies: method A – direct complex immobilisation; method B – functionalisation of the HMS with 3-aminopropyltriethoxysilane (APTES) followed by the complex immobilisation; and method C – treatment of the APTES functionalised support prepared by method B with trimethylethoxysilane (TMS) to deactivate eventually unreacted surface silanol groups, followed by complex grafting. All the materials were characterised by nitrogen elemental analysis, XPS, FTIR, N 2 adsorption isotherms at −196 °C and the [VO(acac) 2] based materials were also characterised by vanadium ICP-AES analysis. The results indicated that, in method B, APTES was successfully grafted onto the HMS with 90% of efficiency and allowed the covalent attachment of [VO(acac) 2] complex mainly in the inner pores with an efficiency of 65%. In method C, a lower complex immobilisation efficiency was obtained, c.a. 25%, but the complex was covalently bonded throughout the functionalised material. In the case of method A, the parent HMS material immobilised a very low quantity of vanadium complex (2% of efficiency), mainly in the external surface through non-covalent interactions. The catalytic activity of [VO(acac) 2] based materials in the epoxidation of geraniol using tert-butyl hydroperoxide ( t-BuOOH) as oxygen source was assessed. The selectivities of the two epoxides formed in the heterogeneous phase reactions were similar to those observed in the homogeneous phase and the major reaction product was always 2,3-epoxygeraniol. The catalyst which allowed higher substrate conversion was obtained by method B but, when considering the leaching of the active phase, method C produced the most efficient catalyst.