Mesoporous Hybrid Materials Research Articles

Eu3+, Tb3+/β-diketonate functionalized mesoporous SBA-15/GaN composites: Multi-component chemical bonding assembly, characterization, and luminescence

GaN-functionalized rare earth (Eu3+ and Tb3+) organic/inorganic mesoporous nanocomposites have been successfully synthesized (designated as RE(LSBA-15)3(LGaN); RE=Eu, Tb; L=TAASi, BTASi). The organosilane precursor materials (LSBA-15) are synthesized by co-condensation of tetraethylorthosilicate (TEOS) and the functionalized β-diketones (TAASi and BTASi) in the presence of Pluronic P123 surfactant as a template. The modified β-diketones ligands are also used to covalently bond with surface-modified GaN and formed another precursor LGaN. Both of the precursors can coordinate with rare earth ions to synthesize the final mesoporous materials via a sol–gel process. FTIR, TEM, XRD, and nitrogen (N2) adsorption/desorption measurements are employed to characterize the mesostructure of RE(LSBA-15)3(LGaN). The luminescence properties and thermogravimetric analysis of all the prepared materials are characterized in detail, and the results reveal that a series of uniformed mesopore structure hybrid materials has been achieved. The mesoporous material Eu(BTASiSBA-15)3(BTASiGaN) has better luminescence intensity, higher quantum efficiency, and longer lifetime than Eu(TAASiSBA-15)3(TAASiGaN). While the nanocomposite Tb(TAASiSBA-15)3(TAASiGaN) revealed the strongest characteristic emission of Tb3+ ions than Tb(BTASiSBA-15)3(BTASiGaN), the excellent luminescent properties and thermal stability enable the hybrid mesoporous material to have potential applications in optical field.

Synthesis and Optical Properties of Organic-Inorganic Hybrid Mesoporous Materials with Naphthalene Bridging Groups

Ordered naphthalene-bridged hybrid periodic mesoporous organosilicas (PMOs) were synthesized by co-condensation of 2,7-bis(3-triethoxysilylpropylaminocarbonyloxy) naphthalene (NIS) and tetraethoxy orthosilane (TEOS) using cationic trimeric surfactant [C10H21N+ (CH 3)2 (CH2)2N +(CH3) (C10H21)(CH2)2N+ (CH3)2C10H21 ] · 3Br as a structure-directing agent.The resulting samples were characterized by powder X-ray diffraction,high resolution transmission electron microscopy,nitrogen adsorption-desorption,and differential scanning calorimetry/thermogravimetric analysis.Ordered mesoporous hybrid materials with a crystal-like pore wall formed when the molar ratio of NIS to the sum of NIS and TEOS was 40%.When this value is below or above 40%,ordered mesoporous hybrid materials with amorphous phase in the pore walls,and nonporous hybrid materials are obtained,respectively.As the number of naphthyl groups in the pore walls increases,the thermal stability of the hybrid materials is enhanced through the strong π-π interactions between organic groups.Because of the fluorescent naphthyl groups in the silica framework,the PMOs exhibit optical behavior consistent with excimer formation.Absorption spectra of the PMOs show blue shifts compared with that of the precursor (NIS),suggesting the formation of aggregates in the pore walls of the hybrid materials.As the molar ratio of NIS to the sum of NIS and TEOS increases,the fluorescence quantum yield of the PMOs decreases through fluorescence quenching caused by aggregation of naphthyl groups.

Fluorogenic detection of Tetryl and TNT explosives using nanoscopic-capped mesoporous hybrid materials

A hybrid capped mesoporous material, which was selectively opened in the presence of Tetryl and TNT, has been synthesised and used for the fluorogenic recognition of these nitroaromatic explosives.

Mesoporous hybrid material composed of Mn3O4nanoparticles on nitrogen-doped graphene for highly efficient oxygen reduction reaction

The hybrid material composed of Mn3O4 nanoparticles on nitrogen-doped graphene was prepared via a solvothermal process and investigated for the first time as a catalyst for oxygen reduction reaction (ORR). Its high ORR activity, excellent durability and tolerance to methanol make this hybrid material a promising candidate for highly efficient ORR in fuel cells and metal-air batteries.

Designing bifunctional acid–base mesoporous hybrid catalysts for cascade reactions

Bifunctional mesoporous hybrid materials, containing both proton sponges and acid groups, have been prepared following different synthetic routes: co-condensation processes (sol–gel or micellar one-pot routes) or post-synthetic grafting of the organic functionalities. 1,8-Bis(dimethylamino)naphthalene (DMAN), a proton sponge with high pKa, was used as an organic functional builder base and 3-mercaptopropyltriethoxysilane (MPTES) as a pendant precursor of sulfonic acids. The bifunctional hybrid materials were extensively characterized and were investigated as heterogeneous catalysts for various one-pot C–C bond-forming cascade reactions such as deacetalization–Knoevenagel condensation or deacetalization–nitroaldol (Henry) reaction.

Ultrahigh-efficiency photocatalysts based on mesoporous Pt–WO3 nanohybrids

A reliable nanocasting method has been developed to synthesize mesoporous hybrids of platinum (Pt) nanoparticles decorating tungsten trioxide (WO3). The process began with modification of the SBA-15 template with carbon polymers and Pt nanoparticles accompanied by adsorption of W(6+), which was then converted into m-Pt-WO3 composites by heat treatment and subsequent template removal. The synthetic strategy can be easily extended to prepare other mesoporous nanohybrids with metal oxide loaded precious metal composites. Comprehensive characterizations suggest that the as-developed m-Pt-WO3 nanohybrid exhibits unique properties with mesoporous structure, excellent crystalline structure, and high surface area. When the photocatalytic properties of m-Pt-WO3 nanohybrids were systematically investigated, it was revealed that the m-Pt-WO3 nanohybrids showed great promise for degrading the organic dye under visible light irradiation, which shows an excellent photocatalytic activity that far exceeded those of pure phase mesoporous WO3 and commercial TiO2 (P25), and was 10-fold more active than that of the bulk Pt-WO3 catalyst. The as-developed synthetic route opens up a new avenue for designing mesoporous hybrid materials for various applications benefiting from the unique porous structure, high surface area, and synergistic effects among constituents.

Heterostructured BaSO4–SiO2 mesoporous materials as new supports for gold nanoparticles in low-temperature CO oxidation

Nanosized BaSO4-based mesoporous hybrid materials have been developed and identified as new efficient inorganic salt-based support systems for ultrastable gold nanoparticles in low-temperature CO oxidation.

Highly sensitive and selective detection of Cu(ii) by periodic mesoporous rhodamine derivative-based organosilicas with crystal-like pore walls

Rhodamine-6G Schiff-base bridged periodic mesoporous organosilicas (RSPMOs) were successfully synthesized by co-condensation of rhodamine Schiff-base derivative-bridged organosilanes and tetraethoxysilane (TEOS), using the ionic liquid 1-hexadecyl-3-methylimidazolium bromide (C16mimBr) as a structure-directing agent. The formation mechanism of ordered mesoporous hybrid materials with crystal-like pore walls was mediated by the self-assembly of both the long-chain ionic liquid and the new organosilane precursors. As the molar fraction of the new organosilane precursors was above 1%, hybrid materials with crystal-like pore walls were obtained, which was due to the face-to-face π–π interaction between rhodamine moieties of the new organosilane precursors within the framework. Little or no fluorescence emission of the hybrid material with rhodamine Schiff-base units was observed because of the existence of spirolactam in rhodamine moieties before chelating with metal ions. However, a dramatic enhancement in fluorescence emission was shown due to opening of the spiro structure in rhodamine moieties, which was induced by intramolecular charge transfer from metal ions to rhodamine units when the hybrid materials chelated with corresponding metal ions. RSPMOs showed high sensitivity and selectivity towards Cu2+ in aqueous solutions with good tolerance for other metal ions, showing great superiority in practical application.

A comparative study on carbon paste electrodes modified with hybrid mesoporous materials for voltammetric analysis of lead (II)

We have chemically functionalized four types of ordered mesoporous silicas (referred to as MPS1–MPS4) with 5-mercapto-1-methyltetrazole (MTTZ), and have incorporated these materials into carbon paste electrodes (CPEs) to obtain sensors for the determination of Pb(II) ion in aqueous media by adsorptive stripping voltammetry. Materials and MPS1–MPS4, were characterized by nitrogen adsorption–desorption measurements, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and elemental analysis. The effect of the mesostructure of the MPS on the performance of the sensors was evaluated with respect to linear ranges, sensitivities, selectivities, precision and limits of detection. The CPE modified with MPS1 (a silica with mesopores of 37Å in diameter and pseudo-spherical particle morphology) exhibited the best inter-electrode reproducibility and sensitivity, a linear range between 1 and 30ppb and a limit of detection of 0.8ppb. The CPE modified with MPS4 (a silica with hexagonal mesopores of 58Å in diameter, cylindrical particle morphology and bigger size) exhibited the poorest inter-electrode reproducibility and sensitivity, a linear range between 5 and 100ppb, and a limit of detection of 2.6ppb. The differences in the voltammetric responses to Pb(II) therefore appear to result from differences in the coating of the inner surface with MTTZ, the pore diameter, and the particle morphology as well as the size of the hybrid MPS. As consequence of its highest inter-electrode reproducibility and sensitivity, good linear range and low limit of detection, MPS1 can be selected as the better material to prepare modified CPE for Pb(II) determination in aqueous media by adsorptive stripping voltammetry.

Novel porous organosilica containing amino and β-cyclodextrin groups

The elaboration of new hybrid mesoporous silica materials containing β-cyclodextrin groups and amine functions is reported. The synthesis is based on a direct co-condensation between β-CDAPS, a hybrid precursor obtained by reaction between tosyl-β-cyclodextrin and aminopropyltrimethoxysilane previously described, and tetraethyl orthosilicate via a sol–gel pathway templated by three different surfactants: anionic (sodium dodecylsulfate), cationic (cetyltrimethylammonium bromide) or neutral (Triton X-45) ones. The chemical structure and morphology are characterized and analyzed for all the series. Finally, the templating based mechanisms are investigated by comparing these samples with series prepared without template or without cyclodextrin.

Hexagonal mesoporous fluorescent hybrid materials with electron acceptor viologen units in the framework

Mesoporous MCM-41-type fluorescent hybrid materials with methylene viologen units in the framework have been synthesized via the co-hydrolysis and -condensation of dichloride of N,N′-bis(triethoxysilylmethyl)-4,4′-bipyridinium (VP) and tetraethoxysilane (TEOS). The obtained hybrid materials are characterized by the small-angle X-ray diffraction (SAXRD), high-resolution transmission electron microscope (HR-TEM), Fourier transform infrared spectrometer (FTIR), solid-state 29Si NMR spectrum, nitrogen adsorption/desorption analyse, diffuse reflectance UV–VIS (DR UV-Vis), and confocal laser scanning fluorescence microscopy (CLSFM). The results show that the VP units are covalently bonded into the silica framework to form mesoporous hybrid materials. The obtained hexagonal mesoporous hybrid materials are found to emit fluorescence at ca.380 nm and 420 nm. The fluorescent intensity enhances with increasing the amount of the VP occupied in the silica framework, and it is not affected by the hexagonal or cubic array of the pore channels. It could be prospected that such hybrid materials would present great potential applications in drug delivery and fluorescence probing for medical diagnosis and synchronous therapy.

Heterogenization of Lanthanum and Neodymium Monophosphacyclopentadienyl Bis(tetramethylaluminate) Complexes onto Periodic Mesoporous Silica SBA-15

The monophosphacyclopentadienyl bis(tetramethylaluminate) lanthanide complexes (η5-PC4Me4)Ln[(μ-Me)2AlMe2]2 and [η5-PC4Me2(SiMe3)2]Ln[(μ-Me)2AlMe2]2 (Ln = La, Nd) have been immobilized onto mesoporous silica SBA-15, which was dehydroxylated at 500 °C. Major reaction pathways comprise methane elimination, that is, silanolysis of Ln(μ-Me)Al moieties with surface silanol groups, and trimethylaluminum separation resulting from donor-induced tetramethylaluminate cleavage. The formation of bis- and monosiloxy surface species is discussed involving transient [(η5-PC4Me4)Ln[(μ-OSi≡)(μ-Me)AlMe2]x[(μ-Me)2AlMe2]2–x] and [{η5-PC4Me2(SiMe3)2}Ln[(μ-OSi≡)(μ-Me)AlMe2]x[(μ-Me)2AlMe2]2–x] (Ln = La, Nd, x = 1, 2) as well as more stable entities such as [(η5-PC4Me2R2)(≡SiO)Ln[(μ-Me)2AlMe2]] and/or [(η5-PC4Me2R2)[(μ-OSi≡)(μ-Me)AlMe2]Ln(Me)] and [(η5-PC4Me2R2)(≡SiO)Ln[(μ-OSi≡)(μ-Me)AlMe2]] and/or [(≡SiO)2Ln(η5-PC4Me2R2)]. Moreover, surface alumination via released trimethylaluminum and the formation of [(≡SiO)3–yAlMey] (with y = 1, 2) surface sites is observed. The organometallic/inorganic hybrid materials (η5-PC4Me2R2)Ln(AlMe4)2@SBA-15-500 have been characterized by DRIFT and solid-state NMR spectroscopy, elemental analysis, and nitrogen physisorption. The equimolar reaction of complex (η5-PC4Me4)Nd[(μ-Me)2AlMe2]2 with tris(tert-butoxy)silanol (HOSi(OtBu)3) produces the siloxide complex (η5-PC4Me4)Nd[{μ-OSi(OtBu)3}(μ-Me)AlMe2][(μ-Me)2AlMe2], which was crystallographically authenticated as a model of a potential monophosphacyclopentadienyl neodymium surface species. All of the mesoporous hybrid materials are moderately active initiators for isoprene polymerization, producing 1,4-cis polyisoprene PI (>99%), which is in contrast to the case for the borate-activated molecular precursors (η5-PC4Me2R2)Ln(AlMe4)2 giving preferentially 1,4-trans PI. The surface organometallic chemistry as well as the polymerization performance markedly depend on the thermal pretreatment of the SBA-15 silica, as shown for the corresponding hybrid materials obtained from SBA-15-200 and SBA-15-700.

A Photoactivated Molecular Gate

Light-controlled gate: A novel capped silica nanoscopic mesoporous hybrid material for photo-driven cargo release applications has been designed and prepared. The capped system, which shows a zero release, contains a photo-cleavable bulky o-methoxybenzylamine derivative. Upon irradiation at 254 nm, photo-degradation of the o-methoxybenzylamine framework and the subsequent delivery of a fluorescent cargo were observed (see figure).

Targeted synthesis of micro–mesoporous hybrid material derived from octaphenylsilsesquioxane building units

A micro–mesoporous inorganic–organic hybrid material PAF-12, derived from octaphenylsilsesquioxane (OPS, [C6H5(SiO1.5)]8) as basic building units, was successfully synthesized via Suzuki cross-coupling reaction. Thermogravimetric analysis (TGA) shows that PAF-12 is thermally stable up to 500°C in air condition. According to Ar sorption isotherm, the network of PAF-12 shows classic type IV isotherm and also exhibits a sharp uptake at low relative pressures indicating micro–mesoporous texture. The pore size distribution of PAF-12 calculated from non-linear density functional theory (NLDFT) gives only two clear narrow peaks centered at 1.57 and 3.17nm. To the best of our knowledge, PAF-12 is the first hybrid material containing both micropore and mesopore reported for silsesquioxane-based materials. Additionally, PAF-12 exhibits high adsorption abilities for organic chemical pollutants such as benzene and methanol. The effects of different solvent systems to synthesize PAF-12 were also investigated and the optimal condition was found out.

Pb (II) removal from aqueous media by EDTA-modified mesoporous silica SBA-15

An organic–inorganic hybrid mesoporous silica material was synthesized by two-step post-grafting method of SBA-15 with 3-aminopropyltrimethoxy-silane (APTES) and thionyl dichloride (SOCl2) activated ethylenediaminetetraacetic acid (EDTA) in sequence and measured by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), elemental analysis (EA), transmission electron microscopy (TEM), nitrogen (N2) adsorption–desorption analysis and back titration. The material was found having the beneficial properties of mesoporous silica SBA-15 and EDTA. Adsorption potential of the material for Pb (II) removal from aqueous solution was investigated by varying experimental conditions such as pH, contact time and initial metal concentration. The removal efficiency of Pb2+ was high under studied experimental conditions. The adsorption equilibrium could be reached within 20min and the kinetic data were fitted well by pseudo-second-order and intraparticle diffusion model. The adsorbent exhibited a favorable performance and its maximum adsorption capacity calculated by the Langmuir model was 273.2mgg−1. Recycling experiments showed the adsorbent could be regenerated by acid treatment without altering its properties. The chemical states of the elements involved in the adsorption were analyzed by X-ray photoelectron spectroscopy (XPS). The results demonstrated that the adsorption mechanism of the material involved Na Pb ion-exchange and carboxyl group dominated surface complexation.

Mesoporous organic–inorganic hybrid aerogels through ultrasonic assisted sol–gel intercalation of silica–PEG in bentonite for effective removal of dyes, volatile organic pollutants and petroleum products from aqueous solution

Hybrid mesoporous materials with high surface area (1144m2/g) and enhanced thermal stability were achieved through ultrasonication assisted sol–gel-intercalation technique using bentonite clay and PEG grafted sol gel silica. Solvent extraction with mixed solvents showed efficient aerogel formation of the hybrids. The products were characterised by small angle X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, zeta potential measurement and BET surface area analysis. The XRD analysis showed interlayer spacing of ∼43.28Å. The increasing spacing is interesting in a way that the available interior pore volume can be tailored for the enhanced adsorption of different pollutants. Clay-hybrid porous materials showed hydrophobic nature with high adsorption capacities for organic dyes (methylene blue and malachite green), volatile organic pollutants (phenol and toluene) and petrochemical derivatives (kerosene, engine oil and diesel). The contact time necessary to attain adsorption equilibrium and the optimum pH were found to be 2h and 5.0–6.0, respectively. Kinetics of adsorption was rapid film diffusion with a pseudo-second-order rate constant. The best interpretation for the equilibrium data was given by the Langmuir isotherm indicative of homogenous surface and maximum adsorption capacity of clay-hybrid towards methylene blue, malachite green, phenol and toluene from aqueous solution was found to be 101.55, 98.42, 116.75 and 114.10mg/g, respectively, and was found to be greater than commercial adsorbents like activated carbon, zeolite and activated alumina. Thermal regeneration studies were carried out by calcinating the exhausted adsorbents. Clay-hybrid aerogels were then demonstrated using different petroleum products to exhibit excellent oil absorption properties.

Synthesis and Catalytic Properties of Hybrid Mesoporous Materials Assembled from Polyhedral and Bridged Silsesquioxane Monomers

A family of hybrid mesoporous materials with high temperature stability was obtained by the suitable covalent combination of two types of siloxane precursors. Specifically, cubic T(8) polyhedral oligomeric (POSS) and aryl bridged silsesquioxane monomers (1,4-bis(triethoxysilyl)benzene, BTEB) play the role of nanobuilders. An optimal molar ratio of the two precursors (5-25 mol% of total silicon content from the BTEB disilane) generated a homogenous, highly accessible, and well-defined mesoporous material with hexagonal symmetry and narrow pore-size distribution. Physicochemical, textural, and spectroscopic analysis corroborated the effective integration and preservation of the two different nanoprecursors, thereby confirming the framework of the mesoporous hybrid materials. A post-synthesis amination treatment allowed the effective incorporation of amino groups onto the aryl linkers, thereby obtaining a stable and recyclable basic catalyst for use in C-C bond-formation processes.

New Luminescent Mesoporous Material Covalent Bonded with Europium (III) Organic/Inorganic/Polymeric Hybrid

Luminescent ternary organic-inorganic-polymeric mesoporous hybrid material Eu-(PA-SBA-15)-PMAA was prepared in situ through hydrothermal and solvothermal method based on hydrolysis and co-polycondensation. The organic ligand PA (O-phthalic anhydride) was modified by silane coupling reagent APS ((3-aminopropyl) triethoxysilane) to generate the precursor PA-Si which was used to form the ordered inorganic Si-O networks through direct co-hydrolysis and co-polycondensation process with SBA-15 in the presence of Pluronic P123 surfactant as a template. TEOS (tetraethoxysilane) was used to promote the hydrolysis and condensation process. Eu3+ complex Eu(PA-Si)3 was covalently linked to the ordered mesoporous SBA-15 and organic polymer PMMA which was synthesized by addition polymerization reaction of the monomer MMA (methyl methacrylate) in the presence of the initiator BPO (benzoyl peroxide). Moreover, the binary organic-inorganic mesoporous hybrid material Eu (PA-SBA-15)3 without polymer was also synthesized simultaneously for comparison. The luminescence properties of the hybrids were characterized in detail. The results show the ternary hybrid exhibits stronger emission intensity, longer lifetime and higher quantum efficiency than binary one which proves that the introduction of the organic polymer PMMA brings improvement to the hybrid system.

Adsorption of Hexavalent Chromium Ions by Organic-Inorganic Hybrid Mesoporous Material in Aqueous Solution

This paper reports the adsorption of Cr(VI) ions from aqueous solution by organic-inorganic hybrid mesoporous material. Adsorbents were prepared with the DTAB,TTAB,CTAB and STAB for organic component synthesis organic-inorganic hybrid mesoporous material(HM), namely HMD, HMT, HMC and HMS. The best adsorption hexavalent chromium experimental conditions is obtained after having orthogonal experiment.

Facile encapsulation of monodispersed silver nanoparticles in mesoporous compounds

A novel method has been developed to fabricate well dispersed silver nanoparticles inside the channels of mesoporous silica. In this method, the mesoporous host (SBA-15), filling agent (toluene) and the Ag precursor (Ag(NH3)2NO3 solution) can be regarded as three chemical “sub-phases” of a system. Cooperative assembly among the system restricted the growth of Ag nanoparticles, in which Ag(NH3)2NO3 solution adsorbed on surfaces of mesoporous host in the form of nano-layer played a key role. Silver particles with small size and monodispersed form could be detected using transmission electron microscopy, confirming also the absence of large particles outside the mesopore system. The particles size and loading amount of Ag nanoparticles in the mesoporous silica could be easily tuned by altering the concentration of Ag(NH3)2NO3 solution. These hybrid mesoporous materials show an excellent catalytic activity toward the reduction of dye molecules by sodium borohydride.