Mesoporous Metal Research Articles

Mesoporous Intermetallic NiAl Nanocompound Prepared in a Molten LiCl Using Calcium Species as Templates

A novel mesoporous intermetallic NiAl nanocompound was successfully prepared at 600 °C in a molten LiCl with an assistance of CaH2. The obtained powder had a fine crystal structure assigned to a single phase intermetallic NiAl. The measured BET surface area was as high as 113.9 m2/g, originating from the mesopores (3.1 nm on average) and the unique crumpled morphology. Calcium species, such as CaH2, Ca(OH)2, CaO and CaCl2, could work as templates in alloying process and they were readily removable by NH4Cl solution rinsing afterwards. As far as we know, this paper is the first report of mesoporous metal aluminide with a defined crystal structure and a high surface area of >100 m2/g.

Mesoporous Mixed Zirconium–Niobium Oxide (Zr6Nb2O17): An Efficient Catalyst for the Phenol Red Bromination 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.

PVA assisted ZnO based mesoporous ternary metal oxides nanomaterials: synthesis, optimization, and evaluation of antibacterial activity

The poly (vinyl alcohol) (PVA) assisted highly mesoporous Zn-Fe-Mn oxides nanomaterials were synthesized using the sol-gel followed by the self-propagation techniques. The UV–vis spectroscopic technique was used to study the optical properties of the materials. The presence of metal-oxygen bond and deposited OH−/H2O species were characterized by FT-IR spectroscopic technique. The porous morphology and elemental analysis were confirmed by the SEM/EDX and further morphological and crystal structure studies were conducted using TEM/HRTEM techniques. The semi-crystallinity and composition analyses were verified from XRD patterns. Using the BET N2 adsorption-desorption analytical techniques; the porosity, specific surface area, and pore diameter enhancements were confirmed. The optima of PVA and precursors percentage were selected with the help of XRD, UV–Vis, and SEM techniques. The potential of the materials towards antibacterial activities was evaluated against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. The 50(0.7) PVA assisted ternary metal oxide nanocomposite (PVA-TMONC) with 125 μg ml−1 concentration showed better inhibition zone for both Escherichia coli and Staphylococcus aureus bacteria, with a value of 28 and 29 mm in diameter, respectively.

Thermo‐Responsive MOF/Polymer Composites for Temperature‐Mediated Water Capture and Release

AbstractWe report an in situ polymerization strategy to incorporate a thermo‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAM), with controlled loadings into the cavity of a mesoporous metal–organic framework (MOF), MIL‐101(Cr). The resulting MOF/polymer composites exhibit an unprecedented temperature‐triggered water capture and release behavior originating from the thermo‐responsive phase transition of the PNIPAM component. This result sheds light on the development of stimuli‐responsive porous adsorbent materials for water capture and heat transfer applications under relatively mild operating conditions.

Water-Stable, Nonsiliceous Hybrid Materials with Tunable Porosity and Functionality: Bridged Titania-Bisphosphonates

Combining the properties of organic and inorganic moieties with high surface areas and pore volumes offers endless possibilities to design materials adapted to a wide range of advanced applications. The vast majority of mesoporous hybrid materials are siliceous materials, and developing low-cost synthetic methodologies leading to water stable nonsiliceous hybrid materials with controlled texture and functionality is essential. We report here an original strategy for the synthesis of mesoporous bridged titania-bisphosphonate hybrids based on a one-step, templateless nonhydrolytic sol–gel route. The reaction of Ti(OiPr)4 and a rigid bisphosphonate ester in the presence of Ac2O leads to the formation of TiO2 anatase nanorods cross-linked by fully condensed bisphosphonate groups. The porosity can be readily adjusted over a wide range by changing the reaction conditions, and very high specific surface areas (up to 720 m2 g–1) and pore volumes (up to 1.85 cm3 g–1) can be reached. The texture is stable in aqueous media between pH 1 and pH 12. Furthermore, accessible functional organic groups can be easily incorporated using either functional bisphosphonates or easily available monophosphonate compounds. The accessibility of bipyridyl organic groups was checked by Cu2+ adsorption from aqueous solutions. The unique combination of texture, functionality, and stability displayed by bridged titania-bisphosphonates makes these promising materials complementary of other hybrid materials such as organosilicas, MOFs, or mesoporous metal phosphonates.

Peanut-like mesoporous tungsten oxides via a synergistic templating strategy for efficient isoprene detection

In this study, a simple and efficient strategy to prepare peanut-like mesoporous tungsten oxide using o-nonylic acid and triblock copolymer PtBA45PS92PEO117 as synergistic templates was developed. Compared to traditional methods for the synthesis of highly ordered mesoporous metal oxides using PS-PEO as a single template, synergistic templates can form new hierarchical structures. The peanut-like tungsten oxide sphere with an open mouth on its surface has two monodisperse microspheres; the diameter range in the long dimension of the mesoporous tungsten oxides is approximately 1.0–2.0 μm. The peanut-like mesoporous tungsten oxide shows good gas-sensing properties toward isoprene with a low concentration (10–50 ppm) at an operating temperature of 205 °C, with the relative humidity of the testing environment at approximately 80%, and at sensing response/recovery times of approximately 12 s and 71 s, respectively. The outstanding selectivity to isoprene is ten and three times greater than that of ethanol and acetone, respectively.

Mesoporous CuO with full spectrum absorption for photothermal conversion in direct absorption solar collectors

Many semiconductors with broad solar spectrum absorption have always been pursuing for the effective photothermal conversion process. However, it is still a challenge to modulate the structural and bandgap of semiconductors to enhance the photothermal activity synergistically. In this work, facile prepared mesoporous CuO displays a narrower bandgap than non-porous CuO, leading to highly efficient solar-thermal conversion. Mesoporous CuO shows obvious broad and strong optical absorption, especially in the visible light region. It is noteworthy that the mesoporous CuO nanofluids exhibit good dispersibility in water. Different concentrations of mesoporous CuO nanofluids have higher temperature rise than non-porous CuO nanofluids. The photothermal conversion efficiency of 50 ppm mesoporous CuO/water nanofluid is 83.66%, compared with 58.86% for 50 ppm CuO/water nanofluid. Mesoporous CuO will bring a new paradigm for mesoporous metal oxide nanofluids as working fluids in direct absorption solar collectors.

Mesoporous Iron-doped MoS2/CoMo2S4 Heterostructures through Organic-Metal Cooperative Interactions on Spherical Micelles for Electrochemical Water Splitting.

Mesoporous metal sulfide hybrid (meso-MoS2/CoMo2S4) materials via a soft-templating approach using diblock copolymer polystyrene-block-poly(acrylic acid) micelles are reported. The formation of the meso-MoS2/CoMo2S4 heterostructures is based on the sophisticated coassembly of dithiooxamide and metal precursors (i.e., Co2+, PMo12), which are subsequently annealed in nitrogen atmosphere to generate the mesoporous material. Decomposing the polymer leaves behind mesopores throughout the spherical MoS2/CoMo2S4 hybrid particles, generating numerous electrochemical active sites in a network of pores that enable faster charge transfer and mass/gas diffusion that enhance the electrocatalytic performance of MoS2/CoMo2S4. Doping the spherical meso-MoS2/CoMo2S4 heterostructures with iron improves the electronic properties of the hybrid meso-Fe-MoS2/CoMo2S4 material and consequently results in its superior electrochemical activities for both hydrogen evolution reaction and oxygen evolution reaction.

Efficient removal of tetracycline hydrochloride from aqueous solution by mesoporous cage MOF-818

MOF-818, a mesoporous cage metal–organic framework, was investigated for the removal of tetracycline hydrochloride (TC) from aqueous environment. The product was characterized by XRD, BET, FESEM, FT-IR, XPS and TGA. The influence of different parameters such as solution pH, contact time, temperature, adsorption dosage, initial TC concentration on the adsorption capacity was investigated. The as-prepared MOF-818 showed rapid removal of TC and with maximum saturated adsorption capacity calculated to be 442.5 mg g−1 at pH 3.32, 323 K. The adsorption isotherms were fitted by Langmuir, and Freundlich models. The kinetic data was analyzed by pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The TC adsorption process followed pseudo-second-order kinetics and best fitted the Langmuir adsorption model. The thermodynamic data showed that the adsorption was a spontaneous and endothermic reaction. A mechanism for TC adsorption was proposed and the chemisorption and π–π interaction was believed to direct the interaction between MOF-818 and TC molecules.

Comparison of Catalytic Activity of Chromium–Benzenedicarboxylate Metal–Organic Framework Based on Various Synthetic Approach

MIL-101(Cr), as a prototypical mesoporous metal–organic framework (MOF), can be facially prepared by involving different modulators to fit various demands. In this paper, a range of MIL-101(Cr) products were prepared under similar conditions. It was found that one of the additives, phenylphosphonic acid (PPOA), could give a stable hierarchical structure material. Compared to other MIL-101(Cr)s, though hierarchical MIL-101(Cr) showed less porosity, it gave a better catalytic performance in the oxidation of indene and 1-dodecene.

Facile solvent deficient synthesis of mesoporous Co3O4 nanoparticles for electrochemical energy storage

High surface area, mesoporous metal oxide nanoparticles play a significant role in the electrochemical charge storage applications. A facile solvent-deficient approach has been reported for synthesis of high surface area, mesoporous Co3O4 nanoparticles for the electrochemical energy storage. A precursor is obtained by grinding hydrated cobalt nitrate salt with ammonium bicarbonate for 25 min without addition of any true solvent. Further, the precursor is annealed at 300 ℃ to obtain Co3O4 from as prepared untreated precursor and after rinsing using deionized water. The XRD, Raman and FTIR spectra revealed the single-phase formation of Co3O4. SEM shows granular-type morphologies with two distinct size for two different samples. The BET analysis confirms mesoporous nature with specific surface area of 135 and 193 m2g−1 for samples obtained from untreated and rinsed precursors. The maximum specific capacitance of Co3O4 obtained from untreated and rinsed samples are 184 and 349 Fg−1. A very fewer equivalent series resistance of 2.24 Ω and 1.91 Ω has been observed, respectively.

Template-free Synthesis of Mesoporous and Crystalline Transition Metal Oxide Nanoplates with Abundant Surface Defects

Summary Mesoporous transition metal oxides with crystalline walls show promising applications in catalysis and energy storage. Syntheses of those crystalline mesoporous oxides, however, currently remain as an unmet challenge because of the large volume shrinkage during crystallization in a sol-gel process. Here, we demonstrate a facile and general template-free method to prepare six mesoporous transition metal oxides, e.g., CuO, CoO, and spinel MCo2O4 (M = Co, Cu, Mn, Zn), with highly crystalline walls and continuous mesopores in the forms of two-dimensional nanoplates or nanosheets. The method is based on the thermal crystalline transformation from basic carbonates to mesoporous metal oxides. The crystal interconversion not only endows the crystallinity and mesoporosity of oxides but also generates abundant surface-step defects that show remarkable enhancement of the catalytic activity of porous oxides. Our method likely provides an alternative paradigm for cost-effective and universal synthesis of crystalline mesoporous oxides beyond the traditional templating methods.

Metal Oxide Oxidation Catalysts as Scaffolds for Perovskite Solar Cells.

Whilst the highest power conversion efficiency (PCE) perovskite solar cell (PSC) devices that have reported to date have been fabricated by high temperature sintering (>500 °C) of mesoporous metal oxide scaffolds, lower temperature processing is desirable for increasing the range of substrates available and also decrease the energy requirements during device manufacture. In this work, titanium dioxide (TiO2) mesoporous scaffolds have been compared with metal oxide oxidation catalysts: cerium dioxide (CeO2) and manganese dioxide (MnO2). For MnO2, to the best of our knowledge, this is the first time a low energy band gap metal oxide has been used as a scaffold in the PSC devices. Thermal gravimetric analysis (TGA) shows that organic binder removal is completed at temperatures of 350 °C and 275 °C for CeO2 and MnO2, respectively. By comparison, the binder removal from TiO2 pastes requires temperatures >500 °C. CH3NH3PbBr3 PSC devices that were fabricated while using MnO2 pastes sintered at 550 °C show slightly improved PCE (η = 3.9%) versus mesoporous TiO2 devices (η = 3.8%) as a result of increased open circuit voltage (Voc). However, the resultant PSC devices showed no efficiency despite apparently complete binder removal during lower temperature (325 °C) sintering using CeO2 or MnO2 pastes.

Synthesis and characterization of mesoporous crystalline copper metal–organic frameworks for electrochemical energy storage application

The mesoporous nanostructure Cu-metal organic frameworks (Cu-MOF-1 and Cu-MOF-2) have been synthesized by a high temperature solvothermal route. The products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface measurement, Thermo gravimetric analysis, scanning electron microscope and Single crystal XRD. The electrochemical properties of these MOF electrodes were examined by using of cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopic techniques. Comparing the results of CV and GCD studies, both those MOFs have shown significant charge storage capacity, while Cu-MOF-2 has showed a specific capacitance greater than Cu-MOF-1. The Cu-MOF-1 and Cu-MOF-2 electrodes showed a maximum specified capacity of 181 and 248 F g−1 respectively at a current density of 1 A g−1 and an extensive cyclic stability of up to 2000 cycles with capacity retention of ~ 90.1%. The electrochemical studies with Cu-MOF electrodes were conducted in 6 M KOH electrolytes. The excellent electrochemical properties of Cu-MOFs can be credited to the large surface area with a high microporous volume of structurally implanted electro-active metallic centres and the rapid transport of ions into electrolytes/electrodes. The results imply that the Cu-MOFs electrode could be the potentially high- performance electrode materials for super capacitor applications.

Mesoporous Metal-Metalloid Amorphous Alloys: The First Synthesis of Open 3D Mesoporous Ni-B Amorphous Alloy Spheres via a Dual Chemical Reduction Method.

Selective hydrogenation of nitriles is an industrially relevant synthetic route for the preparation of primary amines. Amorphous metal-boron alloys have a tunable, glass-like structure that generates a high concentration of unsaturated metal surface atoms that serve as active sites in hydrogenation reactions. Here, a method to create nanoparticles composed of mesoporous 3D networks of amorphous nickel-boron (Ni-B) alloy is reported. The hydrogenation of benzyl cyanide to β-phenylethylamine is used as a model reaction to assess catalytic performance. The mesoporous Ni-B alloy spheres have a turnover frequency value of 11.6 h-1 , which outperforms non-porous Ni-B spheres with the same composition. The bottom-up synthesis of mesoporous transition metal-metalloid alloys expands the possible reactions that these metal architectures can perform while simultaneously incorporating more Earth-abundant catalysts.

Adsorption behavior of a metal organic framework of University in Oslo 67 and its application to the extraction of sulfonamides in meat samples

In this work, a dispersive solid phase extraction (d-SPE) method for sulfonamides (SAs) has been developed using a stable and mesoporous metal organic framework (University in Oslo 67, UiO-67) as adsorbent, which was synthesized by coordination of Zr4+ ions with 4, 4-biphenyl-dicarboxylicacid (H2BPDC) through a facile one-pot method. Owing to the synergistic effects of π-π interaction, hydrogen bonding, hydrophobic interaction and size match between SAs and the adsorbent, the extraction performance of UiO-67 for SAs was obviously improved. The adsorption behavior, evaluated by the kinetic models, showed that the intraparticle diffusion was involved during the adsorption process. The proper match between the pore size of UiO-67 (3.49 nm) and the molecular sizes of SAs (1.1 nm × 0.65 nm) not only allowed SAs to diffuse intraparticle but also permitted them to adjust their configurations to form hydrogen bonding with the UiO-67. By combination with HPLC analysis, a simple, sensitive, accurate and precise method for detection of SAs has been established. The method proposed in this work showed good performances, including wide linearity (14.6–250 ng/g) with high correlation coefficients (R ≥ 0.9991), low limits of detection (LODs, 0.7–6.5 ng/g for all SAs), satisfactory precision (Intra-day RSDs ≤ 3.4%, inter-day RSDs ≤ 4.7%), and high accuracy (recovery: 83.4–103.8%). Furthermore, benefiting from the mesoporous structure and the Zr cluster center as well as the stability, UiO-67 shows great potential to be an excellent adsorbent of SPE for extraction of SAs from other complex matrices.

Generalized synthesis of high surface area mesoporous metal titanates as efficient heterogeneous catalysts

A novel metal dissolution coupled with reverse micelle formation approach is used as a generalized synthesis method for a series of high surface area metal titanates where the metals used are Bi, Mg, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, and Ce. This study reports the highest surface areas published so far. The homogeneous distributions of the metals and titanium are observed in SEM-EDX and TEM mapping. The synthesized materials were comprehensively characterized using PXRD, Raman, nitrogen adsorption isotherms, SEM; EDX, TEM, TEM mapping, TGA, and XPS. The green catalytic oxidation of aniline to nitrosobenzene occurs within 30 min at room temperature when mesoporous W/Ti binary metal oxide is used as the catalyst. The radical mediated catalytic reaction gives excellent yields and the catalyst is reusable up to 4 reaction cycles without losing significant activity.

Integration of Enzymes and Photosensitizers in a Hierarchical Mesoporous Metal-Organic Framework for Light-Driven CO2 Reduction.

Protection of enzymes with synthetic materials is a viable strategy to stabilize, and hence to retain, the reactivity of these highly active biomolecules in non-native environments. Active synthetic supports, coupled to encapsulated enzymes, can enable efficient cascade reactions which are necessary for processes like light-driven CO2 reduction, providing a promising pathway for alternative energy generation. Herein, a semi-artificial system-containing an immobilized enzyme, formate dehydrogenase, in a light harvesting scaffold-is reported for the conversion of CO2 to formic acid using white light. The electron-mediator Cp*Rh(2,2'-bipyridyl-5,5'-dicarboxylic acid)Clwas anchored to the nodes of the metal-organic framework NU-1006 to facilitate ultrafast photo-induced electron transfer when irradiated, leading to the reduction of the coenzyme nicotinamide adenine dinucleotide at a rate of about 28 mM·h-1. Most importantly, the immobilized enzyme utilizes the reduced coenzyme to generate formic acid selectively from CO2 at a high turnover frequency of about 865 h-1 in 24 h. The outcome of this research is the demonstration of a feasible pathway for solar-driven carbon fixation.

Controlled Synthesis of Mesoporous Pt, Pt-Pd and Pt-Pd-Rh Nanoparticles in Aqueous Nonionic Surfactant Solution

Abstract To date, a wide variety of mesoporous metals has been synthesized using self-assembly of polymeric micelles for catalytic and sensing applications. However, systematic study of trimetallic mesoporous alloys has rarely been performed due to their complex nature. Herein, we demonstrate the synthesis of mesoporous PdPtRh particles by a chemical reduction process with the assistance of a block copolymer, Pluronic® F127. Furthermore, we have also systematically characterized these alloys and evaluated their catalytic performance for methanol oxidation reaction (MOR), in comparison to mesoporous Pt and PdPt particles. Among all the prepared catalysts, the mesoporous PdPtRh sample shows the highest electrocatalytic performance for MOR with high conversion efficiency and tolerance for intermediate generation as well as excellent stability.

Mesoporous Molybdenum-Tungsten Mixed Metal Oxide: A Solid Acid Catalyst for Green, Highly Efficient sp3-sp2 C-C Coupling Reactions.

A mesoporous molybdenum tungsten mixed metal oxide with high surface area (173 m2/g) was synthesized by using metal dissolution coupled with a surfactant assisted reverse micelle formation synthesis method. Comprehensive characterization of the mixed oxide was performed by using PXRD, Raman, BET, SEM, EDX, TEM, and XPS. Thus, the formation of α-Mo0.5W0.5O3 with a homogeneous distribution of Mo and W throughout the material was seen. Furthermore, multiple oxidation states of molybdenum (Mo6+ and Mo5+) and a single oxidation state of tungsten (W6+) were observed. The weak/moderate acidic sites present in the mixed metal oxide resulted in excellent catalytic properties toward the sp3-sp2 carbon-carbon coupling reactions. The coupling of benzyl alcohol and toluene was completed within 15 min at 110 °C with 99% yield.