Uniform Mesopore Size Research Articles

High performance Pd catalysts supported on bimodal mesopore silica for the catalytic oxidation of toluene

A series of bimodal mesoporous silica (BMS-x)-supported Pd catalysts were successfully prepared by a facile sol-gel approach, followed by an impregnation method. The synthesized catalysts were characterized by several analytical techniques and the oxidation of toluene was used to evaluate their catalytic performance. Textural analysis showed that all samples had high surface areas (∼1000 m2/g), large pore volumes (∼1.2 cm3/g) and uniform mesopore size (∼2.6 nm). Defining the level of ammonia solution to within a certain range resulted in the catalysts possessing a typical bimodal mesoporous structure with an intraparticle framework mesopore and an interparticle textural mesopore (18–40 nm). Transmission electron microscopy observations and CO chemisorption results revealed that this unique bimodal mesoporous structure helped to decrease the particle size of Pd nanoparticles and could further enhance their dispersion. Activity tests revealed the Pd/BMS-5–Pd/BMS-20 catalysts with a bimodal mesopore structure possessed superior catalytic performance for the oxidation of toluene compared to Pd/BMS-30 with a unimodal mesopore structure. More importantly, compared with the Pd/MCM-41 and Pd/MCM-48 catalysts, Pd/BMS-15 had improved hydrothermal stability and catalytic performance at a high gas hourly space velocity of 70000 h−1. These results indicate the potential application of the catalysts for the elimination of volatile organic compounds.

Applications of inorganic–organic mesoporous materials constructed by self-assembly processes for removal of benzo[k]fluoranthene and benzo[b]fluoranthene

The mesoporous materials MCM-41 and the functionalized inorganic–organic material p-aminobenzoic acid-MCM-41 (PABA-MCM-41) were used as adsorbents to remove the PAHs benzo[k]fluoranthene and benzo[b]fluoranthene from aqueous media. Both MCM-41 and PABA-MCM-41 exhibited the hexagonal mesostructures typical of the M41S family, as confirmed by SAXS, with type IV isotherms and type H1 hysteresis. The materials showed uniform mesopore size distributions, high surface areas, and thermal stability. Adsorption tests showed that for both mesoporous materials, the quantity adsorbed (q e) increased for higher initial PAH concentrations, and adsorption equilibrium was reached in around 90 min. The experimental kinetic data were fitted using the pseudo-second-order model, and the adsorption process could be described by the Langmuir isotherm. At higher temperatures, there were increases in the initial rates of adsorption and the kinetic constants for adsorption of the PAHs by PABA-MCM-41. The thermodynamic parameters indicated that the process was spontaneous, endothermic, and with a tendency toward disorder of the system at the adsorbent/adsorbate interface. The functionalization of MCM-41 increased the efficiency of adsorption of the PAHs by 44.5 and 32.0 % for benzo[k]fluoranthene and benzo[b]fluoranthene, respectively. Effect of contact time on adsorption of (a) B[k]F and (b) B[b]F by PABA-MCM-41. Conditions: 0.05 g of PABA-MCM-41, 5 mL of each PAH solution (concentration 200 µg L−1), temperature of 25 °C, contact time of 300 min, and agitation at 150 rpm.

Facile synthesis of high dispersion γ-Fe2O3–Au nanoparticles within mesoporous silica spheres

γ-Fe2O3–Au@m-SiO2 composite were successfully prepared by a facile one-pot method, which showed good magnetic property, high nanoparticles dispersion, uniform mesopore size, high surface area and big pore volume.

Activation of Aryl Chlorides in Water under Phase-Transfer Agent-Free and Ligand-Free Suzuki Coupling by Heterogeneous Palladium Supported on Hybrid Mesoporous Carbon

In this study, heterogeneous palladium catalysts supported on ordered mesoporous cobalt oxide–carbon nanocomposites were applied to the water-mediated Suzuki coupling reaction of chlorobenzene and phenylboronic acid and exhibited a high yield of biphenyl (49%) under mild reaction conditions free of phase-transfer agents and ligands. Product yields in the reaction of aryl chlorides containing electron-withdrawing groups attached to their benzene ring can reach approximately 90%. Thiol-functionalized mesoporous silica, which can trap soluble Pd species, was used to confirm the negligible leaching in solution and therefore heterogeneous reaction. This heterogeneous catalyst is stable, showing unobvious activity loss after 10 catalytic runs. Characterization by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption fine structure analysis, and N2 sorption techniques revealed intercalated CoO nanoparticles inside a carbon matrix with uniform mesopore sizes (∼3 n...

Hydrophilicity-controlled ordered mesoporous carbon for lithium-sulfur batteries.

Ordered mesoporous carbon (OMC) materials were synthesized from a mesoporous silica KIT-6 (3-D cubic la3d meso-structure) as the hard-template via a nano-replication method. Hydrophilic and hydrophobic OMC materials were prepared using different carbon precursors including sucrose (suc-OMC) and phenanthrene (phe-OMC) at different carbonization temperatures of 700 degrees C and 1100 degrees C, respectively. The OMC materials thus obtained exhibit high surface areas, uniform mesopore sizes and highly ordered meso-structure. To investigate the hydrophilicity effect of OMC materials on the performance of lithium-sulfur battery, we prepared the samples having different ratios of the suc-OMC to phe-OMC, which were 100:0, 75:25, 50:50, 25:75 and 0:100. As a result, the mixed OMC materials (with ratios of 75:25, 50:50 and 25:75) exhibited better cycle performances, compared to those of the suc-OMC and phe-OMC.

Solid–solid grinding/templating route to magnetically separable nitrogen-doped mesoporous carbon for the removal of Cu2+ ions

N-doped ordered mesoporous carbon materials (NOMC) with 2D hexagonal symmetry structure were synthesized via a facile solid–solid grinding/templating route, in which the ionic liquids (ILs) of 1-cyanoethyl-3-methylimidazolium chloride and SBA-15 were employed as the precursor and hard template, respectively. The as-synthesized NOMC features with a uniform mesoporous size (3.5nm), ropes-like morphology (0.4–1μm in length) and high surface area (803m2/g). The quantitative analysis revealed the nitrogen content on the surface of NOMC is 5.5at%. Magnetic iron nanoparticles were successfully embedded into the carbon matrix by introducing iron chloride to the mixture of SBA-15 and ILs during the synthesis process. The NOMC-Fe composite possessed superior adsorption capacity of Cu2+ ions (23.6mg/g). Kinetic and isothermal analysis demonstrated the strong interactions between Cu2+ ion and the adsorbent. Furthermore, the composite was magnetically separable from solution under an external magnetic field and thus displayed a superior reusability in the recycling test.

Highly Ordered Mesoporous Tungsten Oxides with a Large Pore Size and Crystalline Framework for H2S Sensing

AbstractAn ordered mesoporous WO3 material with a highly crystalline framework was synthesized by using amphiphilic poly(ethylene oxide)‐b‐polystyrene (PEO‐b‐PS) diblock copolymers as a structure‐directing agent through a solvent‐evaporation‐induced self‐assembly method combined with a simple template‐carbonization strategy. The obtained mesoporous WO3 materials have a large uniform mesopore size (ca. 10.9 nm) and a high surface area (ca. 121 m2 g−1). The mesoporous WO3‐based H2S gas sensor shows an excellent performance for H2S sensing at low concentration (0.25 ppm) with fast response (2 s) and recovery (38 s). The high mesoporosity and continuous crystalline framework are responsible for the excellent performance in H2S sensing.

Aggregation-Free Gold Nanoparticles in Ordered Mesoporous Carbons: Toward Highly Active and Stable Heterogeneous Catalysts

A coordination-assisted synthetic approach is reported here for the synthesis of highly active and stable gold nanoparticle catalysts in ordered mesoporous carbon materials using triblock copolymer F127 as a structure-directing agent, thiol-containing silane as a coordination agent, HAuCl4 as a gold source, and phenolic resin as a carbon source. Upon carbonization, the gold precursor becomes reduced to form monodispersed Au nanoparticles of ca. 9.0 nm, which are entrapped or confined by the "rigid" mesoporous carbonaceous framework. Nanoparticle aggregation is inhibited even at a high temperature of 600 °C. After removal of the silica component, the materials possess the ordered mesostructure, high surface area (~1800 m(2)/g), large pore volume (~1.19 cm(3)/g), and uniform bimodal mesopore size (<2.0 and 4.0 nm). The monodispersed gold nanoparticles are highly exposed because of the interpenetrated bimodal pores in the carbon framework, which exhibit excellent catalytic performance. A completely selective conversion of benzyl alcohol in water to benzoic acid can be achieved at 90 °C and 1 MPa oxygen. Benzyl alcohol can also be quantitatively converted to benzoic acid at 60 °C even under an atmospheric pressure, showing great advantages in green chemistry. The catalysts are stable, poison resistant, and reusable with little activity loss due to metal leaching. The silane coupling agent played several functions in this approach: (1) coordinating with gold species by the thiol group to benefit formation of monodispersed Au nanoparticles; (2) reacting with phenolic resins by silanol groups to form relatively "rigid" composite framework; (3) pore-forming agent to generate secondary pores in carbon pore walls, which lead to higher surface area, larger pore volumes, and higher accessibility to to the gold nanoparticles. Complete removal of the silica component proves to have little effect on the catalytic performance of entrapped Au nanoparticles.

Synthesis of highly graphitic mesoporous carbon using Ni–Fe double-layered hydroxide as both template and catalyst precursor

A graphitic mesoporous carbon was prepared using sucrose as carbon precursor and Ni–Fe (Ni/Fe = 2) double-layered hydroxide (DLH) as template and catalyst precursor by a solid-phase method. The material was characterized by X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. Results indicated that the graphitic mesoporous carbon has a uniform mesopore size and a high degree of graphitization. The mesoporous structure of the carbon is generated by templating from the mesoporous DLH. The catalytic metallic Ni was formed by reduction of Ni ions in the pore walls of the DLH with carbon during carbonization, and this caused graphitized carbon to be formed at a quite low temperature of 900 °C. [New Carbon Materials 2013, 28(2): 121–126]

Adsorption of Methylene Blue from Aqueous Solution by Periodic Mesoporous Titanium Phosphonate Materials

Periodic mesoporous titanium phosphonate (PMTP-1) materials were synthesized and used as an adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. The PMTP-1 powder has a uniform mesopore size of 2.9 nm with high surface area of 606 m2/g. The batch-dye adsorption experiments were performed under various conditions including contact time, adsorbent dose, initial MB concentration, solution pH and temperature. The adsorption equilibrium was achieved after 30 minutes of contact time, and the adsorption of MB on PMTP-1 was best fitted to the Langmuir isotherm model with the maximum monolayer adsorption capacity of 617.28 mg/g. Thermodynamic parameters such as ΔG, ΔH and ΔS were calculated. Results of kinetic studies indicated that the adsorption process followed the pseudo-second-order model, which suggests that the process might be a chemisorption. The study results indicate that the PMTP-1 powder could be used as an efficient adsorbent for the removal of textile dyes from e...

Synthesis of highly graphitic mesoporous carbon using Ni-Fe double-layered hydroxide as both template and catalyst precursor

A graphitic mesoporous carbon was prepared using sucrose as carbon precursor and Ni-Fe (Ni/Fe=2) double-layered hydroxide (DLH) as template and catalyst precursor by a solid-phase method. The material was characterized by X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. Results indicated that the graphitic mesoporous carbon has a uniform mesopore size and a high degree of graphitization. The mesoporous structure of the carbon is generated by templating from the mesoporous DLH. The catalytic metallic Ni was formed by reduction of Ni ions in the pore walls of the DLH with carbon during carbonization, and this caused graphitized carbon to be formed at a quite low temperature of 900 °C.

Functional mesoporous bioactive glass nanospheres: synthesis, high loading efficiency, controllable delivery of doxorubicin and inhibitory effect on bone cancer cells.

Controllable drug delivery is one of the important ways for the therapy of bone cancer. Conventional mesoporous silica nano-particles may lack dual properties for combining controllable delivery of anti-cancer drugs and bone-forming bioactivity for bone cancer therapy. The aim of this study is to synthesize mesoporous bioactive glass (MBG) nanospheres with combined dual functions of bioactivity and controlled drug delivery, and to further investigate their delivery property of anti-cancer drugs as well as the functional effect on bone-cancer cells. MBG nanospheres with spherical morphology and internal mesoporous microstructures were successfully prepared by a facile hydrothermal method. The prepared MBG nanospheres possess high specific surface area and mesopore volume (443 m2 g-1, 0.57 cm3 g-1) as well as uniform mesopore size distribution (2.9 nm). The MBG nanospheres demonstrate excellent bioactivity by inducing apatite mineralization in simulated body fluids. An anti-cancer drug, doxorubicin hydrochloride (DOX), was successfully loaded in the MBG nanospheres with a distinctively high loading efficiency of around 90%. The loading amount of DOX can be effectively controlled by adjusting the initial drug-loading concentrations. MBG nanospheres can maintain a sustained release of DOX, and their release kinetics can be controlled by varying the pH microenvironment and initial drug-loading concentrations. In addition, the prepared MBG nanospheres showed obvious degradation by releasing Ca2+ and SiO4 4- ions in PBS. Furthermore, the delivery of DOX from MBG nanospheres into cell culture environment shows a significant inhibitory effect on the viability of osteosarcoma cells with the increase of interaction time. The prepared MBG nanospheres have high specific surface area and mesopore volume, excellent apatite-mineralization ability, distinct degradability, high DOX-loading efficiency and controllable DOX release as well as anti-cancer functions. These unique characteristics suggest that the obtained MBG nanospheres may be used for the therapy of bone cancer.

Superhydrophilic mesoporous sulfonated melamine–formaldehyde resin supported palladium nanoparticles as an efficient catalyst for biofuel upgrade

Mesoporous sulfonated melamine–formaldehyde resin (MSMF) has been successfully synthesized from the self-assembly of a copolymer surfactant (F127) with a mixture of melamine, formaldehyde and NaHSO3 in an aqueous solution. After removal of the copolymer surfactant (F127) by ethanol extraction, the MSMF exhibits uniform mesopore sizes centered at 10.2 nm. The contact angle (0°) of water on the sample shows that the MSMF is superhydrophilic. After impregnating with a Pd species, a MSMF supported Pd catalyst (Pd/MSMF) is obtained, which shows high activity and excellent recyclability in an important model reaction for biofuel upgrade (hydrodeoxygenation of vanillin), compared with a conventional carbon supported Pd catalyst (Pd/C). The superior catalytic properties of the Pd/MSMF catalyst should be potentially important for biofuel upgrades in the future.

Synthesis and CO2 capture properties of mesoporous carbon nitride materials

Mesoporous carbon nitride (MCN) and carbon nitride–carbon (MCN/C) composites with a partly graphitized structure are synthesized by using mesoporous silica SBA-15 as a hard template and ethylenediamine and carbon tetrachloride as precursors, possessing uniform mesopore size of 6.3nm, high surface area of 278–338m2/g, and high nitrogen content of 20.5–24.9% with abundant basic sites. The synthesized MCN and MCN/C composites are used as adsorbents for CO2 capture, showing high adsorption capacity and good reusability. The presence of carbon coating layer in MCN/C composites introduced more micropores, which favored the capture of CO2, exhibiting high CO2 capture capacity of 3.05mmol/g at 0°C and 2.35mmol/g at 25°C and 760mmHg, with good CO2/N2 selectivity and excellent regeneration stability.

Post-enrichment of nitrogen in soft-templated ordered mesoporous carbon materials for highly efficient phenol removal and CO2 capture

Control of porosity and structure and modification of surface and framework are the golden rules to adapt carbon materials to targeted applications. The former has been fairly well developed for the soft-templated FDU-type mesoporous carbons while there is still a large need for the latter. In this paper, a simple post-synthetic route is adopted to incorporate nitrogen-containing functionalities into the frameworks of these carbon materials. The basic principle relies on the confinement of melamine molecules in the mesochannels of an ordered mesoporous carbon matrix such that they self-condense into carbon nitride uniformly dispersed under a heat treatment at ∼500 °C and subsequently lead to the formation of mesoporous nitrogen-enriched carbon materials at 700–900 °C with well-retained ordered mesostructure and high surface area. The structure, porosity, composition and the nitrogen-containing functionalities are extensively studied. The integration of regular and open mesostructure, uniform and large mesopore size, high mesoporosity, and nitrogen enrichment makes these materials highly efficient for phenol removal, not only through physisorption with fast adsorption kinetics and large capacity but also by a newly found photo-degradation property with remarkable catalytic activity. Furthermore, the mesoporous nitrogen-enriched carbons deliver promising properties for CO2 capture with greatly enhanced heats of adsorption and well-retained high capacity. Given that the FDU-type mesoporous carbon materials hold variable structures, tunable pore sizes, flexible morphologies and an ease for large-scale synthesis, the success in nitrogen-enrichment would significantly accelerate the progress of their practical applications in pollution control, environment management, supercapacitors and fuel cells.

Highly selective epoxidation of styrene over mesoporous Au–Ti–SBA-15 via photocatalysis process: Synthesis, characterization, and catalytic application

Highly ordered Au–Ti–SBA-15 mesoporous molecular sieves were successfully synthesized by one-pot hydrothermal synthesis in acid medium, and were characterized by XRD, UV–vis, SEM, element-mapping, HRTEM, N2 adsorption, XPS, 29Si MAS NMR, NH3-TPD and FT-IR. The as-prepared Au–Ti–SBA-15 samples were possessed of highly ordered mesostructures with larger pore diameter, pore volume and uniform mesopore size distribution. In the oxidation of styrene with H2O2 as the oxidant over Au–Ti–SBA-15 catalyst under photo-irradiation, reaction parameters, such as molar ratio of H2O2 to styrene, reaction time, solvent, the amount of catalyst, catalyst species, and the amount of 3% NaOH, were conditioned at length. As a result, highly selective epoxidation of styrene over catalyst was carried out perfectly for 10min with high TOF of 4.75×103min−1.

Preparation of POSS-based organic–inorganic hybrid mesoporous materials networks through Schiff base chemistry

The synthesis of novel POSS-based organic–inorganic hybrid mesoporous materials networks functionalized with amine groups through Schiff base chemistry is reported. The material shows uniform mesoporous size. Nitrogen sorption analyses give high specific surface areas of 641–1103m2g−1 with pore volumes of 0.47–0.53mLg−1. The combined results of FTIR, solid 13C NMR and 29Si NMR show that the POSS building blocks are successfully weaved in the porous structure without obvious alteration of the POSS structural characteristics. The hybrid materials show excellent thermal stability.

Catalytic production of hydrogen through aqueous-phase reforming over platinum/ordered mesoporous carbon catalysts

A series of platinum catalysts supported on ordered mesoporous carbon (CMK-3) with different Pt loadings from 1 to 10 wt% have been prepared, and their catalytic activities for hydrogen production viaaqueous-phase reforming (APR) of ethylene glycol (EG) have been investigated. Characterization by X-ray powder diffraction, transmission electron microscopy, N2 sorption, and CO chemisorption techniques reveal that an ordered mesostructure, high surface area, large pore volume, and uniform mesopore size in the mesopores are maintained with a high dispersion of platinum nanoparticles after APR of EG at 250 °C under 45 atm over 24 h. These results show that the structure of the ordered mesoporous carbon support exhibits outstanding hydrothermal stability in APR under high pressure and temperature. The APR activities of Pt/CMK-3 catalysts as a function of Pt loading were increased up to 7 wt% Pt loading. The optimum Pt loading was found to be 7 wt%, with a 37.8 cm3gcat−1 min−1hydrogen production rate. The results presented in this work suggest that Pt/CMK-3 is a very efficient catalyst for producing hydrogen in the APR reaction due to good hydrothermal stability with an open mesoporous structure. The findings presented here are expected to provide new opportunities for rational design of heterogeneous carbonaceous catalysts for aqueous-phase reactions under severe reaction conditions.

Effect of different lanthanum source and preparation method on the lanthanum-doped mesoporous SBA-15 synthesis

Lanthanum-substituted mesoporous SBA-15 molecular sieve has been prepared by direct synthesis and post-synthesis procedures using lanthanum nitrate or lanthanum chloride as lanthanum source. Characterizations by atomic absorption, X-ray diffraction, nitrogen adsorption, UV–Vis spectra analysis, FT–IR spectroscopy and scanning electron microscopy have been carried out to evaluate the efficiency of the incorporation of lanthanum by these procedures. Results showed that Lanthanum was well incorporated into the hexagonal framework of SBA-15 molecular sieves by these two procedures. These LaSBA-15 mesoporous molecular sieves retain the hexagonal order and physical properties of siliceous SBA-15 material. Compared to lanthanum chloride, the lanthanum nitrate is a suitable lanthanum source, which can match the hydrolysis rate of silicon precursor and composite materials possess larger specific surface area, uniform mesopore size distribution.

Nanocasting fabrication of ordered mesoporous phenol–formaldehyde resins with various structures and their adsorption performances for basic organic compounds

Highly ordered mesoporous carbonaceous phenol–formaldehyde resins with two-dimensionally (2-D) hexagonal and 3-D bicontinuous cubic mesostructures have been successfully prepared by a simple nanocasting process. We adopted a low-molecular-weight resol as a precursor and mesoporous silica materials SBA-15 and KIT-6 as the hard templates. The resol precursor can be readily infiltrated into the mesochannels of the silica templates and converted to rigid 3-D zeolite-like resin skeletons under a simple heat treatment of 200–500°C without any catalyst. Several factors influencing the mesostructural replication, including the symmetry and texture of the hard templates, the structure and loading amount of the precursor, and the thermopolymerization temperature, are systematically investigated. The results show that better mesopore connectivity, higher thermopolymerization temperature and proper loading amount of the thermosetting resol precursor are essential for faithful mesostructural replication. The structural, textural and framework properties of the ordered mesoporous replicas are fully characterized. It is manifested that the replicas are composed of highly cross-linked phenolic resin frameworks. These mesoporous phenolic resin replicas have high surface areas (up to 1600m2/g) and large pore volume (up to 1.12cm3/g) and uniform mesopore size (3–4nm). When used as adsorbents, the ordered mesoporous carbonaceous phenolic resins exhibit excellent performances for removing toxic basic organic compounds from waste-water, with fast adsorption kinetics, high adsorption affinity and large adsorption capacities.