Mesoporous Metal Research Articles

A mesoporous non-precious metal boride system: synthesis of mesoporous cobalt boride by strictly controlled chemical reduction.

Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO2 into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.

Biomimetic mineralization of nitrile hydratase into a mesoporous cobalt-based metal-organic framework for efficient biocatalysis.

Nitrile hydratases (NHases) have attracted considerable attention owing to their application in the synthesis of valuable amides under mild conditions. However, the poor stability of NHases is still one of the main drawbacks for their industrial application. Recently, mesoporous metal-organic frameworks (MOFs) have been explored as an attractive support material for immobilizing enzymes. Here, we encapsulated a recombinant cobalt-type NHase from Aurantimonas manganoxydans into the cobalt-based MOF ZIF-67 by a biomimetic mineralization strategy. The nano-catalyst NHase1229@ZIF-67 shows high catalytic activity for the hydration of 3-cyanopyridine to nicotinamide, and its specific activity reached 29.5 U mg-1. The NHase1229@ZIF-67 nanoparticles show a significant improvement in the thermal stability of NHase1229. The optimum reaction temperature of NHase1229@ZIF-67 is at 50-55 °C, and it still retained 40% of the maximum activity at 70 °C. However, the free NHase1229 completely lost its catalytic activity at 70 °C. The half-lives of NHase1229@ZIF-67 at 30 and 40 °C were 102.0 h and 26.5 h, respectively. NHase1229@ZIF-67 nanoparticles exhibit an excellent cycling performance, and their catalytic efficiency did not significantly decrease in the initial 6 cycles using 0.9 M 3-cyanopyridine as the substrate. In a fed-batch reaction, NHase1229@ZIF-67 can efficiently hydrate 3-cyanopyridine to nicotinamide, and the space-time yield was calculated to be 110 g·L-1·h-1. Therefore, the cobalt-type NHase was immobilized in MOF ZIF-67, which is shown as a potential nanocatalyst for the large-scale industrial preparation of nicotinamide.

Biomass-derived ordered mesoporous carbon nano-ellipsoid encapsulated metal nanoparticles inside: ideal nanoreactors for shape-selective catalysis

Ordered mesoporous polymers and carbon with a nano-ellipsoid morphology were synthesized by hydrothermal carbonization of biomass derivatives. Their multifunctional features have been demonstrated and the ability of encapsulating metal nanoparticles (NPs) is presented. With the merits of porosity and anchored metal NPs, the hybrid nanocatalyst shows potential for shape-selective hydrogenation.

Chemistry on the electrodes: post-functionalization and stability enhancement of anchored dyes on mesoporous metal oxide photoelectrochemical cells with copper-free Huisgen cycloaddition reaction

Copper-free Huisgen cycloaddition reaction was applied to post grafted dyes on mesoporous electrodes. It enhances the stability towards desorption and offers the possibility of dye functionalization directly performed on the electrodes.

Mixed Metal Oxide Mesoporous Nanoparticles For Environmental Remediation

Mesoporous mixed metal oxides (SnO2(x) -TiO2 (1-x) , x= 0.75,0.50 and 0.25) were synthesized by evaporation induced self assembly using cationic surfactant, Cetyl Trimethyl Ammonium Bromide (CTAB) as the structure directing agent. The small angle X-ray diffraction pattern of mesoporous SnO2 and SnO2-TiO2 mixed metal oxides revealed the presence of well defined mesostructure in the metal oxides. The mixed metal oxide system has crystallized in orthorhombic structure, resembling the host lattice. Mesopore channels were collapsed upon calcinations at 550°C. The optical absorption of the SnO2 has been extended into the visibleregion upon incorporation of “Ti”. A remarkable enhancement of the photocatalytic degradation efficiency (60% ) of (SnO2(0.5) -TiO2 (0.5) was observed against aqueous solution of methylene blue dye.

Facile Preparation of Hydrophilic Mesoporous Metal-Organic Framework via Synergistic Etching and Surface Functionalization for Glycopeptides Analysis.

In view of the size and hydrophilicity of glycopeptides, materials having suitable channels (size-exclusion) and strong hydrophilic surface (hydrophilic interaction) are preferred to enrich the glycopeptides in biological samples. Metal-organic frameworks (MOFs) are good candidates. However, their smaller microporous channels and low chemical stability have limited the application. Herein, a facile strategy was established to construct hydrophilic mesoporous MOF via synergistic etching and surface functionalization by using phytic acid (PA). Besides, polyvinylpyrrolidone (PVP) was added during MOF synthesis to enhance the water stability of the MOF. Owing to the expanded hydrophilic mesoporous channels, the PA-modified Ce-MOF effectively and selectively captured 422 glycopeptides from 155 glycoproteins in tryptic digests of human serum (2 μL). The present work sheds light on the easy fabrication of hydrophilic mesoporous materials, and this established material holds unique advantages for glycopeptides analysis in biological samples.

H5PV2Mo10O40 Polyoxometalate Encapsulated in NU-1000 Metal–Organic Framework for Aerobic Oxidation of a Mustard Gas Simulant

The immobilization of H5PV2Mo10O40 polyoxometalates (POMs) in the in the mesoporous channel-type metal–organic framework (MOF), NU-1000, via simple impregnation method is reported here. Characteriz...

Block copolymer-templated electrodeposition of mesoporous Au-Ni alloy films with tunable composition

The fabrication of mesoporous bimetallic alloys has attracted significant attention in recent years due to their higher catalytic activity and stability compared to monometallic mesoporous metals. In this work, we have utilized the soft-templated electrochemical deposition procedure by electrochemically reducing Au and Ni precursors in the presence of block copolymer micelles to form mesoporous bimetallic Au-Ni films at the appropriate applied potential. The as-prepared mesoporous Au-Ni films exhibit uniform mesopores throughout the entirety of the films without any visible cracks and good distribution of the composing elements. The Au and Ni contents in the mesoporous Au-Ni films can be conveniently controlled by adjusting the compositions of the Au and Ni precursors in the initial precursor solution, respectively. When employed as electrocatalysts for MOR, the mesoporous bimetallic Au-Ni films exhibit significantly enhanced electrocatalytic activity compared to the pure mesoporous Au film due to the synergistic effects arising from the multimetallic component and improved accessibility to the active sites as a result of the mesostructure. These findings highlight the promising potential of the as-prepared mesoporous bimetallic Au-Ni films for practical applications in direct methanol fuel cells (DMFCs).

Ordered mesoporous Pt/Fe3O4–CeO2 heterostructure gel particles with enhanced catalytic performance for the reduction of 4‐nitrophenol

The unique physicochemical properties of ordered mesoporous transition metal oxides have attracted more and more attention. The hydrolysis process of metal oxide precursors is difficult to control, and it is difficult to synthesize an ordered mesoporous transition metal oxide material using the conventional template method. Ordered mesoporous Pt/Fe3O4–CeO2 heterostructure gel materials with excellent catalytic properties were successfully prepared using aerogel technology and the chemical deposition method. The Pt/Fe3O4–CeO2 material was an n–n combined heterostructured semiconductor material which consisted of a magnetic Fe3O4 layer, a CeO2 core and Pt noble metal doped nanoparticles. A layer of Fe3O4 thin film was formed on the surface of ordered mesoporous Pt/CeO2 gel matrix material using the chemical deposition method. The intriguing heterostructural features could facilitate reactant diffusion and exposure of active sites which could enhance synergistic catalytic effects between the Pt nanoparticles and CeO2 nanoparticles. Compared with Pt/CeO2, the prepared Pt/Fe3O4–CeO2 showed enhanced catalytic activity in the reduction of 4‐nitrophenol at room temperature. The catalytic activity of the heterostructure catalysts was systematically investigated using 4‐nitrophenol reduction as a model reaction. The results showed that the Pt (0.1%)/Fe3O4–CeO2 sample exhibited the optimal catalytic performance toward catalytic reduction of 4‐nitrophenol to 4‐aminophenol. The study provided a method for the preparation of heterostructure nanocatalysts with high efficiency, which would be effective for application in various catalytic reactions.

Dual-emitting CsPbX3@ZJU-28 (X = Cl, Br, I) composites with enhanced stability and unique optical properties for multifunctional applications

Abstract Currently, all-inorganic CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) receive great attention due to their spectacular characteristics and optical properties. However, the stability problem greatly restricts the applicability of CsPbX3 QDs. Herein, a novel protection strategy is reported by in-situ growth of CsPbX3 QDs in the mesoporous blue-emitting indium-based metal organic frameworks (ZJU-28). Accordingly, the CsPbX3@ZJU-28 composites possess dual-emission with broad band blue light emission ascribed to π-π* transitions of organic ligands in ZJU-28 and a distinctive narrow peak attributed to the excitonic emission of CsPbX3 QDs. Intriguingly, the CsPbX3@ZJU-28 exhibited both excitation-wavelength dependent and temperature dependent luminescence properties, which make the composites promising for potential application in anti-counterfeiting and temperature sensing. In addition, the ZJU-28 matrix encapsulation give CsPbX3 QDs greatly improved stability, which makes them attractive in LED applications. Therefore, this work will broaden the applicability of CsPbX3 QDs in multifunctional applications, such as anti-counterfeiting, temperature sensing and LEDs.

Preparation and Application of Ordered Mesoporous Metal Oxide Catalytic Materials

The ordered mesoporous metal oxides as catalytic carrier or active center have been reported by many literatures. The large specific surface area and ordered mesoporous structure had caused great concern in the field of catalysis. In the catalytic reaction, the ordered mesoporous materials had great mechanical properties and the active centers had strong interaction between each other. There were obviously advantages of these ordered mesoporous materials than bulk materials or routine nano-materials in the catalytic conversion of volatile organic compound, CO, NOx and other polluting gases. At present, researchers prepared a variety of ordered mesoporous metal oxides by different synthetic methods. Based on the analysis and summary of the literature, this paper briefly reviewed the preparation methods and application of ordered mesoporous metal oxide catalysts and the prospect of future development is worth expecting.

A novel generalized metal dissolution approach for the synthesis of mixed valent mesoporous metal oxides

A novel approach is introduced to synthesize multivalent, mesoporous metal oxides with high surface area using zero oxidation state precursors. Herein, the synthesis and comprehensive characterization of the metal oxides of s block, p block, transition metal, and lanthanide series elements are reported. Some of the synthesized metal oxides showed mixed phases at relatively low temperatures which is advantageous over single-phase materials. The initial metal dissolution process allows this method to be extended to any metal in the periodic table and metal alloys. A green and highly efficient catalytic sp2-sp2 C–C coupling reaction is carried out using high surface area MoO3 (142 m2/g) where complete conversion is observed within one hour.

Comparison of In-Plane Stress Development in Sol-Gel- and Nanoparticle-Derived Mesoporous Metal Oxide Thin Films.

By using an evaporation-induced self-assembly (EISA) process, mesoporous metal oxide thin films are prepared via molecular precursors undergoing a sol-gel transition or by using nanoparticle dispersions as the starting materials. Both methods are employed together with PIB50-b-PEO45 as the structure-directing agent to produce porous TiO2 and ZrO2 thin films with spherical mesopores of around 14 nm in diameter. These nanoparticle- and sol-gel-derived films were investigated in terms of the intrinsic in-plane stress development during the heat treatment up to 500 °C to evaluate the impact of solvent evaporation, template decomposition and crystallization on the mechanical state of the film. The investigation revealed the lowest intrinsic stress for the nanoparticle-derived mesoporous film, which is assigned to the combination of the relaxing effects of the utilized diblock copolymer and the interparticular gaps between the precrystalline nanoparticles. Furthermore, the residual in-plane stress was studied after annealing steps ranging from 300 to 1000 °C and cooling down to room temperature. Here, TiO2 nanoparticle-derived mesoporous films possess a lower residual stress than the sol-gel-derived mesoporous films, while in the case of ZrO2 films, sol-gel-derived coatings reveal the smallest residual stress. The latter is based on the lower thermal expansion coefficient of the dominant monoclinic crystal phase compared to that of the silicon substrate. Hence, the present crystal structure has a strong influence on the mechanical state. The observation in this study helps to further understand the stress-related mechanical properties and the formation of mesoporous metal oxides.

General Way To Construct Micro- and Mesoporous Metal-Organic Framework-Based Porous Liquids.

We report a new class of porous liquids (PLs) using internally functionalized metal-organic framework (MOF) particles as pore carriers and poly(dimethylsiloxane) as bulky solvents. Using a generalizable noncovalent surface-initiated controlled radical polymerization technique, a series of isoreticular UiO-66 particles were dispersed in a liquid PDMS matrix with excellent homogeneity and colloidal stability. Benefiting from the inherent properties of PDMS, the PLs exhibit low vapor pressure, high thermal stability, and fluidity down to -35 °C. Attributed to the bulkiness of PDMS and its inherent high permeability, the sorption properties of the MOF fillers can be largely retained in their respective PLs as confirmed by low-pressure CO2, N2, Xe, and H2O sorption isotherms. The permanent porosity of the PLs can also be largely preserved even after 15 months of storage. Finally, we demonstrate that by tuning the molecular weight and polymer chain architecture of PDMS, it is possible to preserve the permanent porosity of a mesoporous MOF, MIL-101(Cr), within a PL.

A general method to produce mesoporous oxide spherical particles through an aerosol method from aqueous solutions

Mesoporous transition metal oxides (MTMO) with large surface area, nanocrystalline framework, and controlled porosity have brilliant prospects in fields such as energy, environment, catalysis, or nanomedicine. However, the green, reproducible, and scalable production of MTMO are still a bottleneck for their industrial applications. Although spray-drying methods permit to obtain MTMO in a potentially scalable fashion, the use of highly acidic alcoholic precursor solutions presents two main limitations: corrosion and flammability, which hinder their production in large quantities and lower cost. In this work, we present a general, reproducible, simple, and environment-friendly aerosol method for the synthesis of spherical MTMO particles from mildly acidic aqueous solutions. Acetylacetonate and acetate are used as condensation-controlling agents. Mixed oxides of high valence cations (M(IV) such as Ti, Zr, Ce, and their mixed oxides) were prepared with a yield over 95%, virtually without changing the formulation of the precursor mixture, which can be extended potentially to M(III) or M(V) oxides. The replacement of organic solvents by water allows working in air atmosphere, making this approach much safer, cheaper and environmentally friendly than the current aerosol-based routes. We also present the beneficial effect of mesoporous titania spheres as an additive to nickel electrodes used in the hydrogen evolution reaction, as a demonstrator to potential applications. A threefold increase in the electrocatalytic hydrogen production is observed in mesoporous titania-modified nickel electrodes with respect to a pure nickel catalyst. This performance can be further improved ~25% upon UVA-visible irradiation, due to the photoelectrocatalytic effect of the mesoporous TiO2.

Mesoporous Zirconium-Niobium Mixed Oxide (Zr6Nb2O17): an Effective Catalyst Towards Bromination of Phenol Red Reaction

In search for the improved catalytic efficacy, considerable attention has been focused on mixed metal oxides in the last decade. The present study reports catalytic activity of mesoporous mixed metal oxide, Zr6Nb2O17 for the first time. In this study, the mesoporous Zr6Nb2O17 has been synthesized through a soft template based wet chemical approach. The mesoporous Zr6Nb2O17 is realized after the removal of surfactant through calcination at 500 °C, and preserves its mesoporosity after crystallization by heat-treatment at 550 °C. The synthesized oxide exhibits surface area as high as 221 m2/g and pore size of 3.3 nm with narrow pore size distribution. The synthesized mesoporous Zr6Nb2O17 shows significant catalytic activity for the bromination of phenol red. Careful structural characterizations and catalytic activity studies of the mesoporous Zr6Nb2O17 are documented in this report.

Rational Design of Metal Oxide Solid Acids for Sugar Conversion

Aqueous-phase acid-catalyzed reactions are essential for the conversion of cellulose-based biomass into chemicals. Brønsted acid and Lewis acid play important roles for these reactions, including hydrolysis of saccharides, isomerization and epimerization of aldoses, conversion of d-glucose into 5-hydroxymethylfurfural, cyclodehydration of sugar alcohols and conversion of trioses into lactic acid. A variety of metal oxide solid acids has been developed and applied for the conversion of sugars so far. The catalytic activity is mainly dependent on the structures and types of solid acids. Amorphous metal oxides possess coordinatively unsaturated metal sites that function as Lewis acid sites while some crystal metal oxides have strong Brønsted acid sites. This review introduces several types of metal oxide solid acids, such as layered metal oxides, metal oxide nanosheet aggregates, mesoporous metal oxides, amorphous metal oxides and supported metal oxides for sugar conversions.

Abundant hydrogen production over well dispersed nickel nanoparticles confined in mesoporous metal oxides in partial oxidation of methane

To improve the stability of Ni catalysts and employ reactive oxygen species in reducible metal oxides, the Ni nanoparticles were confined within mesoporous metal oxides (La2O3, Yb2O3, ZrO2, CeO2) via evaporation-induced self assembly technique utilizing 3D honeycomb-like silica as substrate for partial oxidation of methane (POM). Compared with supported catalysts, the prepared catalysts showed superior catalysts stability especially 3D honeycomb-like ZrO2 and CeO2 supported Ni catalysts (Ni/3HL-ZrO2-SiO2 and Ni/3HL-CeO2-SiO2) due to confinement effect and strong interaction between Ni and metal oxides. CH4 conversion reached 90%–92%. Outstanding catalytic activity was attributed to highly dispersity of active metal. More importantly, abundant hydrogen production was observed over mesoporous CeO2, ZrO2 supported catalysts and the ratio of H2/CO changed from nominal value 2 to 3. DFT theoretical calculations illuminated structural defect sites of reducible support like CeO2, ZrO2 afforded generation of surface hydroxyl group, which can be regenerated by activation of water and reoxidation of CeO2, ZrO2. Hydroxyl group was beneficial to accelerate greatly water gas shift reaction, promoting the production of hydrogen. This may provide a strategy to regulate production composition of POM to expand its downstream process.

Nanometric morpho-structural characterization of mesoporous metal oxide semiconductors for chemo-resistive gas sensors

SnO2 and ZnO are among the most studied semiconductor oxides for applications as gas sensing devices for detecting and monitoring the presence of toxic gases such as CO, NO, NO2. Enhanced sensing properties have been recently reported on gas sensor based on SnO2-ZnO composites due to the formation of hetero-junction between ZnO and SnO2 grains and the contribution of a depleted layer at the intergrain ZnO-SnO2 interfaces. The sensing characteristics can be further improved by adding metallic nanoparticles with a catalytic activity, like Pt or Pd. Along with the electrical properties of such a complex system, morphology plays an essential role in facilitating and enhancing the interaction with the surrounding gas. In our work, ZnO doped SnO2 mesoporous system for gas sensors has been prepared using solvothermal methods in various experimental conditions. Aiming for a proper optimization of the gas sensing properties, the above mentioned system has been decorated with Pd using wet spray method. This work presents an in depth structural and morphological study by combined techniques of analytical electron microscopy on the mesoporous SnO2-ZnO systems decorated with Pd in function of the synthesis conditions. Electron tomography has been employed for a complete, 3D investigation of the Pd clusters distribution within the mesoporous SnO2-ZnO matrix. By a proper image segmentation Pd clusters have been successfully isolated in the surrounding ZnO-doped SnO2 matrix, thus allowing more complex correlations between the micro/nano-structure and the gas sensing properties.

On the thermal stability of mesoporous metal oxide systems decorated with metallic nanoparticles for gas sensing applications

Mesoporous metal oxide systems decorated with metallic nanoparticles are among the most studied functional materials for their applications as chemo-resistive gas sensors. The temperature at which such materials are supposed to operate as gas sensors in real working conditions for an optimum device sensitivity ranges around 150-300oC. In our work, SnO2 mesoporous systems have been prepared by solvothermal methods. As a method for tailoring the chemo-resistive properties, the obtained mesoporous matrix has been further decorated with metallic Fe nanoparticles by wet spraying methods. The as-prepared systems have been extensively investigated by analytical transmission electron microscopy using a JEOL ARM200F instrument equipped with X-ray Energy Dispersive and Electron Energy Loss spectrometers (EDS/EELS). Our work has been focused on the morphological and structural aspects of the above mentioned system under the influence of in-situ heating up to 550oC (a meaningful temperature from the point of view of sample preparation). The morpho-structural evolution with temperature has been emphasized by High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED), Scanning Transmission Electron Microscopy (STEM) and Electron Energy Loss Spectroscopy Spectrum Imaging (EELS-SI).