Well-defined Mesoporosity Research Articles

Interventions to the Spontaneous Fabrication of Hierarchical ZSM-5 Zeolites by Fluorination-Alkaline Treatment

The sequential fluorination-alkaline treatment protocol has been applied for the tailoring of siliceous ZSM-5 zeolite. The original spontaneous growth of mesoporosity in alkaline medium is altered due to the antecedent fluorination step. The outcome is demonstrated by the apparent delay in the mesoporosity growth, whose essential duration for the well-defined mesoporosity is therefore extended from 30 min to 60 min. A low fluorination level decelerates the mesoporosity growth, whereas a high fluorination level enables the achievement of the mesoporosity. These impacts are closely linked with the alteration to the states of Al sites as the function of fluorination level. Compared to the states of Al sites in the pristine and steamed zeolites, the electronic and steric consequences on the environment of Al species by fluorination is proposed for the interplay with the alkaline medium for the mesoporosity growth.

Structurally Asymmetric Porous Carbon Materials with Ordered Top Surface Layers from Nonequilibrium Block Copolymer Self-Assembly

Inorganic materials with asymmetric pore structures provide increased accessibility and flux, making them attractive for applications in energy conversion and storage, separations, and catalysis. Non-equilibrium-based block copolymer structure-directed self-assembly approaches provide routes to obtaining such materials. We report a one-pot synthesis using the co-assembly and non-solvent-induced phase separation (CNIPS) of poly(isoprene)-b-poly(styrene)-b-poly(4-vinylpyridine) (ISV) triblock terpolymer and phenol formaldehyde resols. After heat-treatment, carbon materials with asymmetric pore structures result. They have a mesoporous top surface atop a porous support with graded porosity along the film normal. The walls of the macroporous support are also mesoporous, providing an additional structural hierarchy and increased specific surface area. We demonstrate how successfully navigating the pathway complexity associated with the nonequilibrium approach of CNIPS enables switching from disordered to ordered top surfaces in the as-made organic–organic hybrids and resulting carbon materials after thermal treatments. To that end, a combination of ex situ transmission small-angle X-ray scattering (SAXS) of the membrane dope solutions, in situ grazing-incidence SAXS (GISAXS) after dope solution blading and during solvent evaporation, and scanning electron microscopy (SEM) of the final membrane structures was used. We expect the final porous carbon materials exhibiting a combination of asymmetric, hierarchical pore structures and well-defined mesoporosity throughout the material to be of interest for a number of applications, including batteries, fuel cells, electrochemical double-layer capacitors, and as catalyst supports.

Alkene-modified Fe3O4 nanoparticle-mediated construction of functionalized mesoporous poly(ionic liquid)s: Synergistic catalysis of mesoporous confinement effect and hydrogen proton for organic transformations

Abstract The preparation of mesoporous poly(ionic liquid)s (MPILs) is critically fundamental for the design of heterogeneous catalysts, whereas traditional methods are difficult to obtain these materials with both well-defined mesoporous structure and unique functionality. Here, HClO4-functionalized MPILs with well-defined mesoporous structure were successfully fabricated, in which the alkene-modified Fe3O4 nanoparticles as structural reinforcer play a vital role for mesoporous structure formation. The MPILs were characterized by N2 adsorption/desorption, scanning electron microscope (SEM), transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and vibration sample magnetometry (VSM), and the results confirm that MPILs possess moderate surface area, well-defined mesoporosity, abundant active ionic centers, as well as efficient magnetic recovery. The resulting MPILs show excellent catalytic activity for condensation reaction and Knoevenagel condensation. The kinetic study reveals that the excellent catalytic activity of MPILs is attributed to the synergistic catalysis of mesoporous confinement effect and hydrogen proton from MPILs, albeit with mass transfer resistance produced by mesoporous channels. Further, the catalyst can be recovered using an external magnetic field and reused at least 10 times without a considerable decrease in its catalytic activity. Finally, alkene-modified Fe3O4 nanoparticle-mediated mesoporous construction promotes a textural engineering approach to the development of novel mesoporous materials for other applications.

Materials Combining Asymmetric Pore Structures with Well-Defined Mesoporosity for Energy Storage and Conversion.

Porous materials design often faces a trade-off between the requirements of high internal surface area and high reagent flux. Inorganic materials with asymmetric/hierarchical pore structures or well-defined mesopores have been tested to overcome this trade-off, but success has remained limited when the strategies are employed individually. Here, the attributes of both strategies are combined and a scalable path to porous titanium nitride (TiN) and carbon membranes that are conducting (TiN, carbon) or superconducting (TiN) is demonstrated. These materials exhibit a combination of asymmetric, hierarchical pore structures and well-defined mesoporosity throughout the material. Fast transport through such TiN materials as an electrochemical double-layer capacitor provides a substantial improvement in capacity retention at high scan rates, resulting in state-of-the-art power density (28.2 kW kg-1) at competitive energy density (7.3 W-h kg-1). In the case of carbon membranes, a record-setting power density (287.9 kW kg-1) at 14.5 W-h kg-1 is reported. Results suggest distinct advantages of such pore architectures for energy storage and conversion applications and provide an advanced avenue for addressing the trade-off between high-surface-area and high-flux requirements.

Controlled synthesis of mesoporous single-crystalline TiO2 nanoparticles for efficient photocatalytic H2 evolution

Mesoporous single-crystals have emerged as a unique family of functional materials, exhibiting excellent performance in various applications, owing to their well-defined accessible mesoporosity and highly single-crystalline structures. Precise tailoring structures of mesoporous single-crystals at the nanoscale remains an unsolved scientific and technical challenge. Herein, we report a facile and general approach for the synthesis of mesoporous single-crystalline TiO2 nanoparticles (designated as MSC-TNs) with distinctive traits including tunable morphologies, controllable particle sizes, well dispersity, high hydrophilicity, well-defined mesoporosity and single-crystal nature. Specifically, the amount of water employed in the precursor solution was seen to give fine control over the particle sizes and morphologies of MSC-TNs. MSC-TNs with different sizes show excellent photocatalytic activity in production of hydrogen from water. Under the illumination of 300 W Xe lamp, MSC-TNs were shown to provide good photodegradation performance with Rhodamine 6 G, as well as H2 production when loaded 1 wt % Pt. In a CH3OH solution H2 was evolved with a rate of 8.98 mmol h−1 g−1, which is significantly higher than with commercial P25 nanoparticles (4.02 mmol h−1 g−1).

Time-Resolved Dynamics of Intracrystalline Mesoporosity Generation in USY Zeolite

The treatment of zeolites with surfactants in alkaline media is an effective and versatile technique to impart intracrystalline well-defined mesoporosity in these materials. In this study, the dynamics of surface reconstruction that occurs during the treatment of USY zeolite by surfactant-templating was monitored in situ by atomic force microscopy. The development of surfactant-templated mesoporosity and the concurrent healing of defects that are characteristic of steamed zeolites occur in less than 1 h at room temperature, which emphasizes the low energy barriers needed to reorganize the crystalline structure of this zeolite. This transformation was also followed by X-ray diffraction, N2 adsorption, and transmission electron microscopy analysis of ultramicrotomed samples to confirm that the rapid formation of surfactant-templated mesoporosity and the reconstruction of the zeolite crystals occur not only on the surface of the zeolite but also homogeneously throughout the whole zeolite. This process involv...

Strategies for Localizing Multiple Functional Groups in Mesoporous Silica Particles through a One-Pot Synthesis

The process of postcondensation for the functionalization of mesoporous silica is based on the cooperation between the end-on growth of arrays of silica nanochannels and the steric hindrance of the functional silanes (R-silanes). To obtain particles with differently functionalized surfaces (thiol and amino groups), the delayed addition of another R-silane was introduced. This tandem postcondensation approach allows for three selective functionalization strategies, depending on the mobility and the steric hindrance of the R-silanes. Following these one-pot synthesis strategies, functional groups can be placed independently on the pore entrances and on the internal surface of the mesoporous silica particles. Confocal laser scanning microscopy was used to image the functional group distribution after selective coupling with a fluorescent dye. Nitrogen sorption measurements were conducted to confirm the well-defined mesoporosity of the functionalized products.

Relaxing volume stress and promoting active sites in vertically grown 2D layered mesoporous MoS2(1-x)Se2x/rGO composites with enhanced capability and stability for lithium ion batteries

In this paper, an effective strategy to fabricate mesoporous MoS2(1-x)Se2x composites supported on graphene sheets (meso-MoS2(1-x)Se2x/rGO) for use as anode materials for lithium ion batteries (LIBs) is reported. The meso-MoS2(1-x)Se2x/rGO composites possess a two-dimensional (2D) layered structure with well-defined mesoporosity and the MoS2(1-x)Se2x nanoparticles are perpendicularly grown on graphene sheets. Due to the merits of 2D layered structural configuration and sulfur-selenium coupled effect, the meso-MoS2(1-x)Se2x/rGO composites promise the enhanced electrochemical performance for LIBs. Introduction of Se may widen the spacing of the (002) crystal plane, as a result, rendering them more effective diffusion path for both Li+ and e− during the charge and discharge process. More importantly, Se incorporation may further induce the transition of meso-MoS2(1-x)Se2x from 2H phase to more metallic 1 T phase. As such, the meso-MoS1.12Se0.88/rGO electrodes exhibit efficient rate capability and good cycling stability with an optimum capacity of 830 mA h g−1 at a current density of 100 mA g−1 for 150th cycle. The meso-MoS1.12Se0.88/rGO electrode still keeps a capacity of 415.3 mA h g−1 even when the current density is 1000 mA g−1 making them promising for potential practical application. The novel synthetic strategy may be applicable to fabricate a large variety of 2D layered chalcogenide electrode materials for LIBs.

Ethane-bridged hybrid monoliths with well-defined mesoporosity and great stability for high-performance peptide separation

A novel kind of hybrid monolith with well-defined mesopore structure was prepared based on sol-gel condensation of 1, 2-bis(trimethoxysilyl)ethane (BTME) and tetramethoxysilane. Compared with terminal organosiloxanes used for preparation of conventional hybrid monoliths, BTME, as an ethane-bridged alkoxysilane precursor, could not only maintain the uniformity of pore size distribution, but also improve the chemical stability of the monolith via Si-C bonds in the framework. Owing to the controllable mesoporous structure and good stability, the monolithic column was used for the separation of peptides with half peak width less than 6 s and the run-to-run and column-to-column relative standard deviations (RSD) for the retention time of five standard peptides less than 2.5%, showing narrow peak width and good reproducibility. Moreover, the separation performance could be well maintained even after washed by the mobile phase with pH 11.0 at 50 °C. Furthermore, 100 cm-length monolithic column was prepared and successfully used for nanoRPLC-ESI-MS/MS analysis of HeLa cell lysate digests, and 5670 proteins corresponding to 37574 peptides were identified from 750 ng of the sample, showing great promising of “single-shot” large-scale in-depth proteomic research.

Magnetic Mesoporous Silica/Chitosan/Polyproline: A Novel Nanocomposite Toward Sensing of Some Clinically Relevant Biomolecules

In this paper, free-radical polymerization inside magnetic mesoporous silica has been investigated in order to open a route to functional polymer–silica composite nanomaterials with well-defined mesoporosity. Proline monomers integrated with chitosan (CS) were electropolymerized into amino-functionalized magnetic mesoporous silica. The fabrication of polyproline-amino-functionalized magnetic mesoporous silica–CS nanohybrid on glassy carbon electrode (GCE) was performed using one step electrodeposition regime. Field emission scanning electron microscopy (FE-SEM) was confirmed as produced nanohybrid material containing polyproline (PPR) into the pores of magnetic (Fe3O[Formula: see text] mobile crystalline material-41 grafted with 3-aminopropyl groups (MMS) which leads to increase of surface coverage of PPR. The results indicate that PPR was successfully generated inside the pores of the amino-functionalized Mobil Composition of Matter No. 41 (nPrNH2-MCM-41) and that the amine group was capable of protonating the polymer, producing polyproline, the most conductive one, without the addition of another acid source during the polymerization step. Therefore, it was evaluated some electrochemical aspects of the prepared nanohybrid using cyclic voltammetry, differential pulse voltammetry and linear sweep voltammetry. Finally, the electroactivity of polyproline -Fe3O4-nPrNH2-MCM-41-chitosan nanohybrid (PPR-MMS-CS) modified GCE toward detection and determination of some clinically relevant small biomolecules was studied.

Facile Control of the Porous Structure of Larch-Derived Mesoporous Carbons via Self-Assembly for Supercapacitors.

Mesoporous carbons have been successfully synthesized via self-assembly using larch-based resins as precursors and triblock copolymers as soft templates. The porous structure of mesoporous carbons can be tailored by adjusting the ratio of hydrophilic/hydrophobic (EO/PO) units owing to interfacial curvature. Interestingly, the porous structures show a distinct change from vortex-like to worm-like pores, to stripe-like pores, and to ordered two-dimensional hexagonal pores as the ratio of hydrophilic/hydrophobic units increases, indicating the significant effect of EO/PO ratio on the porous structure. The mesoporous carbons as supercapacitor electrodes exhibit superior electrochemical capacitive performance and a high degree of reversibility after 2000 cycles for supercapacitors due to the well-defined mesoporosity of the carbon materials. Meanwhile, the superior carbon has a high specific capacitance of 107 F·g−1 in 6 M KOH at a current density of 10 A·g−1.

Metalloporphyrin-Encapsulated Biodegradable Nanosystems for Highly Efficient Magnetic Resonance Imaging-Guided Sonodynamic Cancer Therapy.

Traditional photodynamic therapy (PDT) suffers from the critical issues of low tissue-penetrating depth of light and potential phototoxicity, which are expected to be solved by developing new dynamic therapy-based therapeutic modalities such as sonodynamic therapy (SDT). In this work, we report on the design/fabrication of a high-performance multifunctional nanoparticulate sonosensitizer for efficient in vivo magnetic resonance imaging (MRI)-guided SDT against cancer. The developed approach takes the structural and compositional features of mesoporous organosilica-based nanosystems for the fabrication of sonosensitizers with intriguing theranostic performance. The well-defined mesoporosity facilitates the high loading of organic sonosensitizers (protoporphyrin, PpIX) and further chelating of paramagnetic transitional metal Mn ions based on metalloporphyrin chemistry (MnPpIX). The mesoporous structure of large surface area also maximizes the accessibility of water molecules to the encapsulated paramagnetic Mn ions, endowing the composite sonosensitizers with markedly high MRI performance (r1 = 9.43 mM-1 s-2) for SDT guidance and monitoring. Importantly, the developed multifunctional sonosensitizers (HMONs-MnPpIX-PEG) with controllable biodegradation behavior and high biocompatibility show distinctively high SDT efficiency for inducing the cancer-cell death in vitro and suppressing the tumor growth in vivo. This report provides a paradigm that nanotechnology-enhanced SDT based on elaborately designed high-performance multifunctional sonosensitizers will pave a new way for efficient cancer treatment by fully taking the advantages (noninvasiveness, convenience, cost-effectiveness, etc.) of ultrasound therapy and quickly developing nanomedicine.

Probing Interconnectivity in Hierarchical Microporous/Mesoporous Materials Using Adsorption and Nuclear Magnetic Resonance Diffusion

Adsorption and transport in hierarchical materials are investigated by means of adsorption and nuclear magnetic resonance experiments. Using micro/mesoporous zeolites with well-defined mesoporosity, we show that adsorption at a given pressure can be described as a simple linear combination of the adsorbed amounts taken at the same pressure for the pure microporous (zeolite FAU-Y) and mesoporous (Al-MCM-41) solids. Such a quantitative decomposition allows us to demonstrate the ability of diffusion measurements by Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR) to probe interconnectivity in hierarchical solids. On the one hand, transport in the mechanical mixtures can be described as the superimposition of diffusion in pure microporous and mesoporous solids. On the other hand, PFG NMR for the hierarchical sample provides an effective diffusivity that is intermediate between those for the pure zeolite and mesoporous silica. Furthermore, this effective diffusivity is slower than the linear combinat...

ChemInform Abstract: Mesoporous Non‐siliceous Inorganic—Organic Hybrids: A Promising Platform for Designing Multifunctional Materials

AbstractReview: 150 refs.

Highly dispersed photoactive zinc oxide nanoparticles on mesoporous phosphonated titania hybrid

Mesoporous phosphonated titania hybrid material was prepared with the use of aminotri(methylene phosphonic acid) as the coupling molecule and triblock copolymer F127 as the template, possessing irregular mesostructure formed by nanoparticle assembly of crystalline anatase phase. The phosphonate groups were homogeneously anchored on the mesoporous titania, allowing monolayer adsorption of Zn2+ by extensive coordination with the organic bridging groups. The highly dispersed photoactive ZnO components were then obtained by low-temperature annealing of the Zn2+ adsorbed mesoporous phosphonated TiO2, which exhibited excellent photocatalytic activity with high stability in photo-degradation of Rhodamine B under both UV and visible light irradiation. In comparison with the pristine mesoporous phosphonate titania, the commercial titania P25, and the ZnO/mesoporous titania prepared by the conventional impregnation, the superior photocatalytic performance and stability of the coupled catalyst of ZnO nanoparticles highly dispersed on the mesoporous phosphonated titania might be due to the coupling effect, the well-defined mesoporosity and the incorporation of phosphonic moieties into the TiO2 network, presenting the potential applications in the fields of environmental remediation and solar cells.

Sonochemistry-assisted synthesis and optical properties of mesoporous ZnS nanomaterials

Zinc sulfide (ZnS) nanomaterials with well-defined mesoporosity were synthesized with the assistance of sonochemistry in an ethanol system of Zn(NO3)2 and Na2S, without using any templates or surfactants. The prepared ZnS presented a crystalline structure of the cubic zinc-blende phase and possessed a high specific surface area of 263 m2 g−1 with a narrow pore size distribution around 5.1 nm. Abundant surface defects existed in the obtained mesoporous ZnS, thanks to the NaNO3 salt protection through the process of occasional precipitation in the alcohol system. Sonochemically synthesized ZnS nanomaterials showed higher activities for the photodegradation of Rhodamine B under UV light irradiation than the ones prepared in the absence of sonochemistry or in an aqueous system, which was mainly due to the well-structured mesoporosity and the surface defects.

Towards the control of intercrystalline mesoporosity in inorganic microporous materials: The case of CoAPO-5

The generation of mesoporosity in microporous materials has been postulated as a valid strategy to limit the diffusional problems of organic substrates within the pores of these materials, without affecting their intrinsic catalytic behavior. This article shows the effect of systematic variations of different synthesis parameters on the nature of the intercrystalline mesoporosity in CoAPO-5 materials. The hard impositions of this approach, including a structure-directing agent (SDA) possessing enough structural specificity towards AFI materials under a very wide range of synthesis conditions, and at the same time having the ability of generating intercrystalline mesoporosity, severely reduces the possible choices. Fortunately, N-methyldicyclohexylamine (MCHA) simultaneously obeys both conditions. We have examined some parameters conventionally affecting the crystallization process such as time, temperature and dilution, and some other parameters with particular effect on the results of the crystallization of microporous materials such as heteroatom content, heteroatom source, pH of the starting gel and heating source (conventional or assisted by microwave radiation). Except Co source, the rest of the parameters did have a significant influence on the nature and/or magnitude of intracrystalline mesoporosity. The effect of pH and dilution was particularly relevant, so that ordered intracrystalline mesoporosity is favored when CoAPO-5 is crystallized from relatively diluted and acidic gels. In addition, high Co content produces a higher and better-defined mesoporosity, although it implies a modification of the catalytic activity as the number of active centers is inherently varied. Finally, a relevant improvement in the mesoporosity is obtained when heating is assisted by microwave radiation, since the resultant CoAPO-5 is composed by smaller crystals efficiently and orderly agglomerated in pseudospherical particles with a well-defined mesoporosity of narrower pores.

Well-defined mesoporosity on lignocellulosic-derived activated carbons

Activated carbons with a highly developed mesoscale cavitation-linked structure have been prepared from natural products (e.g. peach stones) by combining chemical and physical activation processes. Characterization results show that these materials exhibit a large “apparent” surface area (∼1500 m 2/g) together with a well-defined mesoporous structure, i.e. large cavities connected to the external surface through narrower mesoporous necks (cavitation effects).

One‐Step Preparation of Efficient and Reusable SO42−/ZrO2‐Based Hybrid Solid Catalysts Functionalized by Alkyl‐Bridged Organosilica Moieties for Biodiesel Production

A series of mesoporous sulfated zirconia materials functionalized by alkyl-bridged organosilica moieties (SO(4)(2-)/ZrO(2)-SiO(2)(R) with various S/Si or Zr/Si molar ratios and R=CH(2)CH(2) or C(6)H(4)) were developed by a one-step co-condensation technique combined with hydrothermal treatment with the aid of a triblock copolymer surfactant (P123). The structures, morphologies, porosities, and acid properties of the materials were well characterized. Subsequently, the catalytic performances (activity and stability) of SO(4)(2-)/ZrO(2)-SiO(2)(R) were evaluated by the transesterification of both pure triglyceride (tripalmitin) and low-cost virgin plant oil (Eruca sativa Gars. oil) with methanol for biodiesel production under mild conditions (atmospheric pressure, 65 °C), and the enhanced catalytic activity with respect to alkyl-free sulfated zirconia was obtained. This excellent catalytic activity was explained in terms of the inherent Brønsted acidity, well-defined mesoporosity, and increased hydrophobicity of the as-prepared, hybrid, solid acid catalyst.

Speciation of Copper in Spherical Mesoporous Silicates: From the Microscale to Angstrom

MCM-41 type mesoporous silicate particles with spherical morphology containing copper nanospecies were synthesized by conventional hydrothermal synthesis. A narrow distribution of silicate particle sizes between 2 and 3 μm and a well-defined mesoporosity were evidenced by electronic microscopy, even for loadings of copper of about 10 wt %. Moreover, CuO nanoparticles ∼30 nm in diameter occluded in the amorphous silica, possibly filling some secondary mesoporosity, were also detected. By Fourier transform infrared spectroscopy with pyridine adsorption and UV−vis diffuse reflectance spectroscopy measurements together with reduction experiments under H2 flow, a detailed study about the relationship between copper loading degree and the acid properties with the local isolated Cuδ+ species surroundings was performed. The incorporation of copper into the silica framework generated surface Lewis acid sites which increase with copper content. The origin of these acid sites could be attributed to the presence of isolated Cuδ+ species possibly coordinated with the framework oxygen atoms. It is noteworthy that Brønsted acid sites were not detected in our materials. By X-ray absorption near edge structure spectroscopy, we determine the coexistence of copper +1 and +2 states. The average coordination numbers calculated from extended X-ray absorption fine structure experiments are consistent with a mixture of nanosized species of copper: CuO nanoparticles, besides isolated Cuδ+ cations located in framework positions with oligonuclear clusters like [Cuδ+···Oδ−···Cuδ+]n in its surroundings, confined within the pores.