Mesoporous Organic Inorganic Hybrid Research Articles

Iron Carbonyl Thiourea Hybrid Material Based on Functionalised Silica from Rice Husk Ash for Oxidation of Limonene

Iron carbonyl thiourea, RHACP1Fe was successfully immobilized onto inorganic silica support from rice husk ask via chloropropyltriethoxysilane (CPTES) and the resulting catalyst was labelled as RHACP1Fe. This mesoporous organic-inorganic hybrid catalyst showed a specific surface area of 245.0 m2g-1. The 29 Si MAS NMR solid state spectrum showed the presence of Q4, Q3, T3 and T2 silicon centres in RHACP1Fe. The oxidation of limonene with H2O2 was studied using RHACP1Fe. A moderate selectivity to the desired product (limonene peroxide) of 67% and a maximum limonene conversion of 60% was achieved. RHACP1Fe could be reused several times without losing its catalytic activity.

Covalently Bonded Ionic Liquid-Type Sulfamic Acid onto SBA-15: SBA-15/NHSO3H as a Highly Active, Reusable, and Selective Green Catalyst for Solvent-Free Synthesis of Polyhydroquinolines and Dihydropyridines

Amine-functionalized ordered mesoporous organic–inorganic hybrid materials are designed as solid supports to covalently immobilize the SO₃H group to achieve sulfamic acid (SBA-15/ NHSO₃H) as a novel catalyst. SBA-15/NHSO₃H as ionic liquid-type heterogeneous catalyst could be separated easily from reaction products and recycled, showing superiority over homogeneous catalysts.

Gravimetric chemical sensors based on silica-based mesoporous organic-inorganic hybrids.

Silica-based mesoporous organic-inorganic hybrid material modified quartz crystal microbalance (QCM) sensors have been examined for their ability to achieve highly sensitive and selective detection. Mesoporous silica SBA-15 serves as an inorganic host with large specific surface area, facilitating gas adsorption, and thus leads to highly sensitive response; while the presence of organic functional groups contributes to the greatly improved specific sensing property. In this work, we summarize our efforts in the rational design and synthesis of novel sensing materials for the detection of hazardous substances, including simulant nerve agent, organic vapor, and heavy metal ion, and develop high-performance QCM-based chemical sensors.

Photofunctional hybrids of lanthanide (Eu3+, Tb3+)/beta-diketonate functionalized MCM-41/SBA-15 mesoporous host prepared with 1,4,7,10-tetraazacyclododecane modified siloxane as covalent linkage

Several kinds of novel lanthanide organic–inorganic mesoporous hybrid luminescent materials have been assembled by introducing the ternary lanthanide ions (Eu3+, Tb3+) and beta-diketone (TTA, TAA) into the functionalized mesoporous hosts through the coordination bond and covalent bond by using 3-chloropropyltriethoxysilane modified 1,4,7,10-tetraazacyclododecane (Cyclen-Si) as an organic bridge molecule. These multicomponent hybrids are characterized by FTIR, TEM, XRD, thermogravimetric analysis, diffuse reflectance UV–Vis spectra and nitrogen adsorption–desorption isotherms, especially the photoluminescence properties of them. The luminescent spectra of the hybrids reveal that the MCM-41 based materials show strong emission intensities, high luminescent quantum efficiencies, long luminescent lifetimes and exhibit characteristic red and green luminescence originated from lanthanide ions (Eu3+ or Tb3+), which suggesting the Cyclen-Si bridge molecule is favorable for the assembly of lanthanide functionalized luminescent hybrids.

Luminescent Hybrids of Eu<sup>3+</sup> Complexes Covalently Bonded with Mesoporous Silica and PMAA

Binary organic-inorganic mesoporous hybrid materials were prepared by covalntly grafting Lanthanide (III) (Eu) trifluoroacetylaceton (TAA) complexes to the ordered meosoporous silica SBA-15 via hydrothermal method and hydrolysis and co-polycondensation method with the surfactant P123 and TEOS. Besides, Novel ternary lanthanide (III) (Eu) organic-inorganic-polymeric mesoporous hybrid materials have been synthesized as well through the introduction of the organic polymer PMAA to the binary system with covalent bond. We investigated the thermal stability and luminescence properties of hybrids and found that the ternary hybrid materials exhibit better thermal stability and stronger emission intensity. Furthermore, compared with the binary mesoporous material Eu (TAA-SBA-15)3, the ternary mesoporous material Eu (TAA-SBA-15)3PMMA exhibits the characteristic emission of the Eu3+ ion with a higher luminescence Intensity, suggesting that the introduction of polymer PMMA into the mesoporous matrix is of benefit for the sensitization of Eu3+ luminescence, by replacing H2O groups that can quench the luminescence of Eu3+ ion.

One-Step Hydrogenation/Esterification Activity Enhancement Over Bifunctional Mesoporous Organic–Inorganic Hybrid Silicas

Bifunctional mesoporous organic–inorganic hybrid silica incorporating both platinum and organosulfonic acid groups were synthesized for use in simultaneously catalyzing the one-step hydrogenation/esterification (OHE) of acetic acid and acetaldehyde, which was considered as a model reaction for the upgrading of biomass-derived bio-oil. The work explored optimizing the synthesis procedure to generate a bifunctional catalyst with enhanced combined activity for the OHE reaction. The presence of Pt was found to enhance the acidic properties of the organosulfonic acid functionalized silica. The mechanism by which the Pt incorporation affected the acid sites was investigated by the using XPS, FT-IR, FT-Raman characterization. The XPS results indicated the presence of electron transfer between the Pt and –SO3H groups. The FT-IR and FT-Raman results, which were in agreement with XPS, demonstrated an electron density increase for S and a S–O bond energy increase, which was proposed to be the reason for the acidity enhancement due to the presence of Pt. Additionally, arenesulfonic acid groups were substituted for propylsulfonic acid groups and the resulting material had higher catalytic activity due to the increased acid strength. An optimal synthesis procedure was demonstrated in which the Pt was first impregnated on the mesoporous silica using reductive deposition. Then Pt was activated and the material further modified by grafting on arenesulfonic acid groups. The resulting catalyst was about four times more active than the original base case bifunctional material.

Organic-Inorganic Hybrid Mesoporous Materials as Regenerable Sensing Systems for the Recognition of Nitroaromatic Explosives.

Fluorescent organic-inorganic mesoporous hybrid materials have been prepared and characterised, and their behaviour against nitroaromatic explosives have been tested. MCM-41 silica was used as an inorganic scaffold and pyrene (P derivative containing trialkoxysilane moieties), dansyl and fluorescein (D and F derivatives also containing trialkoxysilane groups, respectively) fluorophores have been anchored on hybrid materials by a co-condensation method to obtain a homogenous distribution of dyes into the pores of the support. Six sensing materials have been prepared, of which SP, SD, SF were hydrophilic and SPh, SDh, SFh were hydrophobic. Template-free hydrophilic materials (SP, SD, SF) were obtained after repeated NH4 NO3 /ethanol extractions under temperature from as-synthesised (MP, MD and MF supports, respectively) solids. Hydrophobic materials (SPh, SDh, SFh) were prepared by using excess 1,1,1,3,3,3-hexamethyldisilazane with template-free hydrophilic (SP, SD and SF) materials. The six final materials displayed the typical emission bands of the grafted fluorophores. In particular, SP and SPh show the typical pyrene monomer (370-420 nm) and excimer (430-600 nm) emissions. SD and SDh exhibit the broad dansyl fluorescence band in the 450-600 nm range, whereas solids SF and SFh present sharp fluorescein emission centred at 525 nm. The fluorescent behaviour of the six final materials was tested in the presence of explosives (pentaerythritol tetranitrate (PETN), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), nitrobenzene (NB), 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA)). Only nitroaromatic compounds were able to induce emission quenching. As a general trend, the quenching degree depended on the nature of the final material. The best response was obtained with explosives PA and Tetryl, which were able to significantly quench the emission of the sensing supports. The observed quenching was ascribed to the π-π stacking interactions between the electron-donor fluorophores and the electron-withdrawing nitroaromatic explosives. When using SPh for Tetryl and PA, the limits of detection were 8.5 and 1.4 ppm, respectively, whereas they were 14.4 and 1.2 ppm for SDh. Principal component analysis algorithms were applied to the fluorescence measurements taken with the six hybrid materials and the seven explosives. The obtained score plot showed well-defined clusters for the seven explosives tested. Finally, solid SDh was applied to detect trace amounts of Tetryl in soil samples with good results.

Pd(OAc)2@SBA‐15/PrEn nanoreactor: a highly active, reusable and selective phosphine‐free catalyst for Suzuki–Miyauracross‐coupling reaction in aqueous media

A series of ordered mesoporous organic–inorganic hybrid material was designed by using the amine‐functionalized SBA‐15 (PdX2@SBA‐15/NY, Y = 1, 2) as solid support for palladium complexes. Among them, the Pd(OAc)2/ethylenediamine complex encapsulated into SBA‐15 (Pd(OAc)2@SBA‐15/PrEn or Pd(OAc)2@SBA‐15/PrNHEtNH2) exhibits higher activity and selectivity toward Suzuki cross‐coupling reaction under aerobic conditions and water solvent mixture. The SBA‐15/PrEn supported palladium pre‐catalyst could be separated easily from reaction products and used repetitively several times, showing its superiority over homogeneous catalysts for industrial and chemical applications. Copyright © 2013 John Wiley & Sons, Ltd.

Lanthanide‐Functionalized SBA‐15 Mesoporous Hybrids – Ultraviolet‐Visible Excitation and Visible–NIR Emission

9-Hydroxy-2-methyl-phenalenone (MHPO) was synthesized and modified with 3-(triethoxysilyl)propyl isocyanate (TEPIC) through a hydrogen atom addition reaction to achieve a new chemical linkage (named as MHPOSi). SBA-15 mesoporous silica organically functionalized with MHPOSi was synthesized. The MHPOSi was linked to tetraethoxysilane (TEOS) through a condensation process in the presence of Pluronic P123 surfactant as a template. New Ln3+ (Eu3+, Nd3+, Yb3+) organic–inorganic mesoporous hybrid materials were prepared, in which the Ln3+ complexes are covalently attached to SBA-15 and have 1,10-phenanthroline (phen) as a second ligand. The resultant mesoporous hybrids were characterized by FTIR spectroscopy, small-angle X-ray diffraction, N2 adsorption–desorption measurements, thermal analysis, and UV/Vis spectroscopy. They all have high surface areas, uniform mesostructures, and good crystallinity. The photophysical properties of the functionalized mesoporous SBA-15 networks are discussed in detail and they still present excitation capability in the visible region despite the modification of the organic silane. Subsequently, they exhibit characteristic visible (Eu3+) and near-infrared (NIR) luminescence (Nd+ and Yb3+).

Self-assembled hybrid tinphosphonate nanoparticles with bimodal porosity: an insight towards the efficient and selective catalytic process for the synthesis of bioactive 1,4-dihydropyridines under solvent-free conditions

Self-assembled ordered mesoporous organic–inorganic hybrid tinphosphonate nanomaterial (HSnP-2) with crystalline framework structure has been synthesized through the reaction of benzene-1,3,5-triphosphonic acid (BTPA) and Sn(IV) chloride under hydrothermal conditions at 453 K in the absence of any structure directing agent. Powder XRD, FE-SEM, HR-TEM, N2 sorption, solid state 13C CP-MAS and 31P MAS NMR, TG-DTA analysis and FT-IR spectroscopic techniques are employed to characterize the material. The hexagonal crystal phase of the material is established through REFLEX and CELSIZ unit cell refinement programs. The calculated unit cell parameters of HSnP-2 are a = b = 17.515 A and c = 10.254 A. The material is composed of hexagonally ordered tiny nanocrystals of dimensions of ca. 4.0 nm and exhibits high BET surface area (380 m2 g−1), good thermal stability along with uniform supermicropores (ca. 1.3 nm) and an ordered assembly of mesopores. HSnP-2 shows outstanding catalytic activity and high recycling efficiency for the green and efficient one-pot three component coupling reaction for the synthesis of bioactive 1,4-dihydropyridines with excellent yields under solvent-free conditions. The novelty of this eco-friendly catalytic system is further manifested from the mild reaction temperature (333 K) and short reaction time (20 min), together with exclusive selectivity for the desired 1,4-dihydropyridines over 2-arylpyridines or 1,2-dihydopyridines.

Silica-anchored organotin trichloride: a recyclable and clean organotin catalyst for transesterification reactions

A new synthetic scheme towards silica-supported organotrichlorotin derivatives has been developed. It involves the synthesis of (11-triethoxysilyl)undecyltricyclohexyltin, followed by sol-gel processing and, subsequently in the formation of the resulting hybrid silica, by electrophilic substitution of the tricyclohexyltin function by the target grafted trichlorotin using tin tetrachloride. HR-MAS (119)Sn and CP-MAS (29)Si NMR combined with N2-sorption and TEM measurements evidenced the formation of a mesoporous organic-inorganic hybrid silica including a functionally pure supported-organotrichlorotin species. This silica-grafted organotrichlorotin displays a satisfactory catalytic activity in the transesterification of ethyl acetate by 1-octanol. The catalyst could be recycled four times without significant loss of activity. Furthermore, tin leaching below 10 ppm evidences the benefits of the proposed strategy to limit tin contamination of the final products.

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.

Organic–Inorganic Hybrid Mesoporous Polymers Fabricated by Using (CTA)2S2O8 as Self-Decomposed Soft Templates

Organic-inorganic hybrid mesoporous polymers were successfully synthesized by using a template-directed free radical polymerization technique in aqueous solution at 0-5 °C with oxidative complexes as self-decomposed soft templates. The oxidative complexes ((CTA)(2)S(2)O(8)), which were formed between anionic oxidant (S(2)O(8)(2-)) and cationic surfactant (cetyltrimethylammonium bromide, CTAB) at 0-5 °C, can be automatically decomposed due to the reduction of S(2)O(8)(2-). No additional treatment was needed to remove the templates. The reactive functional monomer, 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), was used as main monomer. Styrene was used as the comonomer. With simultaneous free radical copolymerization of TMSPMA and styrene, condensation of methoxysilyl groups, and the self-decomposition of (CTA)(2)S(2)O(8), organic-inorganic hybrid mesoporous polymers were successfully obtained. The mesoporous structures and morphologies of the resultant hybrid mesoporous polymers were found to be strongly dependent on the feed amounts of TMSPMA and styrene. In the absence of styrene, the hybrid polymer PTMSPMA exhibited mesh-like bicontinuous structures with mesopores and high surface area (335 m(2)/g). With the incorporation of styrene, mesoporous nanoparticles were obtained. The surface areas of the mesoporous nanoparticles decreased with the increase of styrene contents. The adsorption capabilities of such mesoporous polymers for organic dye (Congo red) and protein (bovine serum albumin) were also studied.

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.

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.

Enhancement of Pt catalytic activity in the hydrogenation of aldehydes

Bifunctional mesoporous organic–inorganic hybrid silica involving platinum and propylsulfonic acid groups (Pt/SBA15-PrSO 3H) have been demonstrated to have potential for catalyzing the combined one-step hydrogenation/esterification (OHE) reaction. This reaction provides a model system for the catalytic upgrading of biomass-derived bio-oil. In this study, efforts were made to improve the catalytic performance of the catalyst for aldehyde hydrogenation, which was determined to be rate limiting in the OHE reaction with the bifunctional catalyst. STEM analysis coupled with hydrogen chemisorption results showed that aqueous reduction–deposition using formaldehyde as the reducing agent produced highly dispersed platinum nanoparticles located within the mesopores of SBA15. XPS and UV–vis demonstrated that the metal sites were not fully activated due to insufficient reducing capability of the formaldehyde. Elevated temperature treatment of the as-prepared materials in either an air or H 2 environment was examined. These treatments significantly increased the acetaldehyde hydrogenation activity, especially in the case of H 2 treatment. XPS and H 2-TPD results demonstrated that Pt species were further reduced and as a result, hydrogen was activated more readily.

ChemInform Abstract: Organic—Inorganic Hybrid Mesoporous Silica

AbstractReview: 150 refs.

Hybrid organic–inorganic catalytic mesoporous materials with proton sponges as building blocks

Non-ordered organic-inorganic mesoporous hybrid materials with basic sites have been synthesized following a fluoride-catalysed sol-gel process at neutral pH and low temperatures that avoids the use of structural directing agents (SDAs). Proton sponges have been used as the organic builder of the hybrids, while the inorganic part corresponds to silica tetrahedra. The proton sponges are diamines that exhibit very high basicity and, after functionalization, have been introduced as part of the walls of the mesoporous silica by one-pot synthesis. Several hybrids with different organic loadings have been synthesized and characterized by gas adsorption, thermogravimetric and elemental analysis, solid state MAS-NMR and FTIR spectroscopy. These hybrids show high activity as base catalysts and can be recycled.

Vitalising porous inorganic silica networks with organic functions—PMOs and related hybrid materials

Mesoporous organic-inorganic hybrid materials are an interesting class of materials, which combine the advantages of two worlds; the inorganic part builds a robust substrate while organic functions make them alive in a way that they can be potentially used in a number of applications. In this tutorial review, we provide an overview of how mesoporous materials are synthesised via the 'soft template' path and how the incorporation of organic functions can be achieved. Furthermore, a colourful survey full of examples is presented, providing a small overview of field of applications that can potentially benefit from the use of periodic mesoporous organosilicas (PMOs) and related materials.