Preparation Of Mesoporous Metal Oxides Research Articles

Self-organization of unimolecular micelles in beam stream for functional mesoporous metal oxide nanofibers

The use of linear amphiphilic block copolymers as templates is an important method for the preparation of mesoporous materials. However, the obtained assemblies are usually sensitive to synthetic conditions, which impedes the preparation of such mesoporous materials in certain environments. Herein, we report a universal strategy applying an amphiphilic multi-arm triblock copolymer in the preparation of mesoporous metal oxide nanofibers (NFs) using one metal oxide (TiO2, ZrO2, WO3, CeO2), or two (TiO2/WO3, TiO2/ZrO2, TiO2/CeO2) and three (TiO2/WO3/CuO) metal oxides as composites. The template consists of modified β-cyclodextrin as the center of the macromolecule which is attached sequentially to a block of polystyrene, poly(acrylic acid), and poly(ethylene oxide). Under electrospinning conditions, stable unimolecular micelles are formed and effectively co-assemble with metal ions to form fibrous nanostructures. As indicated by various characterization methods, the synthesized TiO2 and its derived composite NFs maintain a straight and continuous fibrous structure after calcination, and TiO2 NFs exhibit uniform mesopores of 10.8 nm in diameter and a large Brunauer-Emmett-Teller surface area of 143.3 m2 g−1. Benefiting from the characteristic structure, still present after modification, Pt-decorated mesoporous TiO2 NFs display excellent ability in the visible-light photocatalytic degradation of tetracycline, which is superior to the commercial P25 catalyst. This study reveals a promising strategy for the preparation of fibrous mesoporous metal oxides.

Single-crystal-like nanoporous spinel oxides: a strategy for synthesis of nanoporous metal oxides utilizing metal-cyanide hybrid coordination polymers.

Development of a new method to synthesize nanoporous metal oxides with highly crystallized frameworks is of great interest because of their wide use in practical applications. Here we demonstrate a thermal decomposition of metal-cyanide hybrid coordination polymers (CPs) to prepare nanoporous metal oxides. During the thermal treatment, the organic units (carbon and nitrogen) are completely removed, and only metal contents are retained to prepare nanoporous metal oxides. The original nanocube shapes are well-retained even after the thermal treatment. When both Fe and Co atoms are contained in the precursors, nanoporous Fe-Co oxide with a highly oriented crystalline framework is obtained. On the other hand, when nanoporous Co oxide and Fe oxide are obtained from Co- and Fe-contacting precursors, their frameworks are amorphous and/or poorly crystallized. Single-crystal-like nanoporous Fe-Co oxide shows a stable magnetic property at room temperature compared to poly-crystalline metal oxides. We further extend this concept to prepare nanoporous metal oxides with hollow interiors. Core-shell heterostructures consisting of different metal-cyanide hybrid CPs are prepared first. Then the cores are dissolved by chemical etching using a hydrochloric acid solution (i.e., the cores are used as sacrificial templates), leading to the formation of hollow interiors in the nanocubes. These hollow nanocubes are also successfully converted to nanoporous metal oxides with hollow interiors by thermal treatment. The present approach is entirely different from the surfactant-templating approaches that traditionally have been utilized for the preparation of mesoporous metal oxides. We believe the present work proves a new way to synthesize nanoporous metal oxides with controlled crystalline frameworks and architectures.

A new type of anionic surfactant with four carboxylates for the preparation of mesoporous materials

In this paper, a new type of anionic surfactant containing four carboxylates was synthesized by a four-step synthetic reaction including bromination reaction and primary amide protective reaction. Intermediates and final products of each step in the whole synthetic process were characterized by 1H NMR and MS. Purification of the anionic surfactant was accomplished through combination of recrystallization and silica gel column chromatography. The structure and the critical micelle concentration (CMC) of this surfactant at different temperatures were also investigated. Unlike traditional monocarboxylate surfactant easy to form lamellar mesostructure, this surfactant has the hexagonal mesophase structure and comparatively low CMC, hopefully to be applied in the preparation of mesoporous metal oxides.

Novel nanocasting method for synthesis of ordered mesoporous metal oxides

Novel one-step high vacuum nanocasting method is developed to prepare ordered mesoporous rare earth and transition metal oxides with high-surface area using mesoporous KIT-6 as hard templates. Characterization of these mesostructured materials was performed by the X-ray powder diffraction, high resolution transmission electron microscopy and N2 adsorption–desorption isotherms. In this synthesis method, metal oxide precursors are effectively filled into the channels of hard templates by a one-step high vacuum impregnation, and the excess precursors can be removed through vacuum filtration. It is a very effective nanocasting method and has the wider application in the preparation of mesoporous metal oxides with high surface area and high purity.

Sonochemistry as a tool for preparation of porous metal oxides

Abstract The porous metal oxides are an important class of materials, because the surface area/volume ratio of a material is increased by many fold, making them very useful in surface-related applications. The mesoporous materials were discovered in the 1990s, and since then they have been excellent candidates for materials science research. These mesoporous materials are prepared by hydrolyzing the inorganic precursor (usually metal alkoxide) in an acid, basic, or neutral medium in the presence of an organic structure-directing agent, the surfactant, in a conventional method. Recently, we have demonstrated that the sonochemical technique can be employed for the synthesis of mesoporous metal oxides. The sonochemical method reduced the time period required for such synthesis by many fold, and also produced more stable structures. We got excellent results with silica, titania, yittria-stabilized zirconia (YSZ), and Fe2O3. We also used an inorganic precursor other than an alkoxide for the preparation of mesoporous metal oxides. In this article, we present some of the recent results on this topic.