Effect of the thermal and hydrothermal treatment on textural properties of Zr-MCM-41 mesoporous molecular sieve

Zr-containing mesoporous molecular sieves were synthesized by hydrothermal method using cetyltrimethyl ammonium bromide as a template and sodium silicate and zirconium sulfate as raw materials. The structure and morphology of the synthesized samples were characterized via various physicochemical methods, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, solid state nuclear magnetic resonance (²⁹Si MAS-NMR) techniques, thermal gravimetric-differential scanning calorimeter (TG-DSC) and N₂ physical adsorption, respectively. The effect of the different initial ZrO₂:SiO₂ molar ratio, the different thermal treatment temperature and the different hydrothermal treatment time on textural property was investigated. The experimental results reveal that the as synthesized samples possess a typical mesoporous structure of MCM-41. On the other hand, the specific surface area and pore volume of the synthesized Zr-MCM-41 mesoporous molecular sieve decrease with the increase of the amount of zirconium incorporated in the starting material, the rise of thermal treatment temperature and the prolonging of hydrothermal treatment time, the mesoporous ordering becomes poor. Also, when the molar ratio of ZrO₂:SiO₂ in the starting material is 0.1, the mesoporous structure of the Zr-MCM-41 mesoporous molecular sieve still retains after calcination at 750 °C for 3 h or hydrothermal treatment at 100 °C for 6 d, and have specific surface areas of 423.9 and 563.9 m²/g, respectively.     

Flatness Properties of S-Posets

We investigate the Galois coverings of weakly shod algebras. For a weakly shod algebra not quasi-tilted of canonical type, we establish a correspondence between its Galois coverings and the Galois coverings of its connecting component. As a consequence we show that a weakly shod algebra which is not quasi-tilted of canonical type is simply connected if and only if its first Hochschild cohomology group vanishes.     

Enhanced Photocatalytic Activity of Titanium Dioxide Supported on Hexagonal Mesoporous Silica at Lower Coverage

The photocatalytic activities of titanium dioxide (TiO₂) supported on hexagonal mesoporous silica (HMS), zeolite Y (NaY) were investigated by using the photodegradation of 2,4,6-trichlorophenol (TCP) as test reactions. It was found that the photocatalytic activity of TiO₂ on HMS was much higher than that of TiO₂ powders, and that of TiO₂ on NaY. It was also found that TiO₂/HMS had maximal photocatalytic activity at a lower Ti content. The larger the pore size of HMS used as the support of TiO₂, the better the photocatalytic activity of TiO₂ for degradating of organic pollutant. These observations suggested that the supported structure was a main factor responsible for enhancement of the photocatalytic activity of TiO₂. Characterization of the samples by TEM, XRD, BET, and UV-vis diffuse reflectance spectra indicated that the structures of HMS and TiO₂ were confirmed and TiO₂ did not enter into the HMS framework and was formed as nanoparticles on all supports.     

Nitrogen‐Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics

Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio‐oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen‐doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and “real‐world” biomass‐derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass‐derived phenolic stream is achieved under conditions of low severity.     

Mesoporous carbon materials: synthesis and modification

Porous carbon materials are of interest in many applications because of their high surface area and physicochemical properties. Conventional syntheses can only produce randomly porous materials, with little control over the pore-size distributions, let alone mesostructures. Recent breakthroughs in the preparation of other porous materials have resulted in the development of methods for the preparation of mesoporous carbon materials with extremely high surface areas and ordered mesostructures, with potential applications as catalysts, separation media, and advanced electronic materials in many scientific disciplines. Current syntheses can be categorized as either hard-template or soft-template methods. Both are examined in this Review along with procedures for surface functionalization of the carbon materials obtained.     

Equilibrium adsorption of a cyclopentane—benzene vapor mixture on active carbon

The data on adsorption of cyclopentane, benzene, and their mixture on active carbon were analyzed by the statistical thermodynamic model. A method to describe the state of a binary mixture in single micropores was offered. A substantial negative deviation from Raoult's law predicted by the concept of an ideal adsorption solution is a consequence of a decrease in the excessive Helmholtz energy brought about by progressive filling when values of the excessive energy are positive over a wide range of adsorption. The excessive values found for the entropy and internal energy of a mixture of molecules in a single micropore are negative due to the heterogeneity of the adsorption field. The approach suggested adequately describes the experimental data and can be used for the determination of differential heats of adsorption. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1070–1076, June, 1999.     

Templated synthesis of electroactive periodic mesoporous organosilica bridged with oligoaniline

The synthesis and characterization of novel electroactive periodic mesoporous organosilica (PMO) are reported. The silsesquioxane precursor, N,N'-bis(4'-(3-triethoxysilylpropylureido)phenyl)-1,4-quinonene-diimine (TSUPQD), was prepared from the emeraldine base of amino-capped aniline trimer (EBAT) using a one-step coupling reaction and was used as an organic silicon source in the co-condensation with tetraethyl orthosilicate (TEOS) in proper ratios. By means of a hydrothermal sol-gel approach with the cationic surfactant cetyltrimethyl-ammonium bromide (CTAB) as the structure-directing template and acetone as the co-solvent for the dissolution of TSUPQD, a series of novel MCM-41 type siliceous materials (TSU-PMOs) were successfully prepared under mild alkaline conditions. The resultant mesoporous organosilica were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry, X-ray diffraction, nitrogen sorption, and transmission electron microscopy (TEM) and showed that this series of TSU-PMOs exhibited hexagonally patterned mesostructures with pore diameters of 2.1-2.8 nm. Although the structural regularity and pore parameters gradually deteriorated with increasing loading of organic bridges, the electrochemical behavior of TSU-PMOs monitored by cyclic voltammetry demonstrated greater electroactivities for samples with higher concentration of the incorporated TSU units.     

Fluorescent Protein Capped Mesoporous Nanoparticles for Intracellular Drug Delivery and Imaging

A multifunctional system for intracellular drug delivery and simultaneous fluorescent imaging was constructed by using histidine‐tagged, cyan fluorescent protein (CFP)‐capped magnetic mesoporous silica nanoparticles (MMSNs). This protein‐capped multifunctional nanostructure is highly biocompatible and does not affect cell viability or proliferation. The CFP acts not only as a capping agent, but also as a fluorescent imaging agent. The nanoassembly was activated by histidine‐based replacement, leading to release of drug molecules encapsulated in the nanopores into the bulk solution. The fluorescent imaging functionality would allow noninvasive tracking of the nanoparticles in the body. By combining the drug delivery with cell‐imaging capability, these nanoparticles may provide valuable multifunctional nanoplatforms for biomedical applications.     

Metal‐Free Oxidation of α‐Hydroxy Ketones to 1,2‐Diketones Catalyzed by Mesoporous Carbon Nitride with Visible Light

As a photocatalyst, mesoporous carbon nitride (mpg‐C₃N₄) shows higher photocatalytic activities in organic synthesis. Herein we report an mpg‐C₃N₄‐catalyzed oxidation of α‐hydroxy ketones to synthesize 1,2‐diketones using visible light. This transformation represents a green and highly efficient synthetic route to synthesize 1,2‐diketones for which catalytic approaches are scarce.