Mesoporous Mixed Metal Oxides Research Articles

Tunable Method for the Preparation of Layered Double Hydroxide Nanoparticles and Mesoporous Mixed Metal Oxide Electrocatalysts for the Oxygen Evolution Reaction.

Preparation of high-performance and durable electrocatalysts for anion exchange membrane water electrolysis is a crucial step toward the broad implementation of this technology. Here, we present an easily tunable, one-step hydrothermal method for the preparation of Ni-based (NiX, X = Co, Fe) layered double hydroxide nanoparticles (LDHNPs) for the oxygen evolution reaction (OER), using tris(hydroxymethyl)aminomethane (Tris-NH2) for particle growth control. The LDHNPs are used as building blocks of mesoporous mixed metal oxides (MMOs) with a block copolymer template (Pluronic F127), followed by thermal treatment at 250 °C. NiX MMOs have a significantly larger surface area compared to the analogous LDHNPs. NiX LDHNPs and MMOs exhibit excellent performance and long-term cycling stability, making them promising OER catalysts. Moreover, this versatile method can be easily tailored and scaled up for the preparation of platinum group metal-free electrocatalysts for other reactions of interest, which highlights the relevance of this work to the field of electrocatalysis.

Enhancing OER Activity of Ni/Co Oxides via Fe/Mn Substitution within Tailored Mesoporous Frameworks

Non-noble mixed metal oxides are promising electrocatalysts for water splitting reactions in alkaline media. The synthesis of complex mixed metal oxides with the desired composition is challenging due to the formation of phase impurities when synthesis is performed via classical approaches. In this work, we applied the nanocasting technique combined with low-temperature calcination (200 °C) in a quasi-sealed container to obtain highly ordered mesoporous mixed metal (Mn/Fe/Ni/Co) oxides. This procedure provides electrocatalysts with distinctive physicochemical characteristics and improved electrocatalytic properties. Partial Ni substitution in Ni0.5Co2.5O4 by Fe and Mn in combination with the highly ordered mesostructure offers a large number of active sites and enhances the performance of the catalyst toward the oxygen evolution reaction (OER) in the alkaline electrolyte. The Mn/Fe/Ni/Co oxide calcined at 200 °C outperforms all other synthesized oxides (current density of 262 mA cm–2 at 1.7 V versus RHE and overpotential of 363 mV at 10 mA cm–2) due to synergistic effects. Moreover, this catalyst exhibits significantly higher activity compared to the oxide of identical composition calcined at higher temperature. The results presented in this work show that tuning the synthesis conditions and composition of mixed metal oxides is a simple way to tailor their surface chemistry, mesoporous structure, and catalytic performance for the OER.

Cover Feature: Incorporation of Cu/Ni in Ordered Mesoporous Co‐Based Spinels to Facilitate Oxygen Evolution and Reduction Reactions in Alkaline Media and Aprotic Li−O2 Batteries (ChemSusChem 5/2022)

The Cover Feature shows the structure of the mesoporous mixed metal oxide bifunctional electrocatalyst with a magnification of the crystalline spinel structure building the framework walls. More information can be found in the Research Article by T. Priamushko et al.

Nanoporous Co/Mn-Mixed Metal Oxides Templated via Polysulfones for Amine Oxidation

Herein, we report syntheses of microporous and mesoporous mixed metal oxides templated via an anionic surfactant. The effects of acid treatment, solvent type, and the amount of metal incorporation ...

Nanocast Mixed Ni–Co–Mn Oxides with Controlled Surface and Pore Structure for Electrochemical Oxygen Evolution Reaction

Nanocasting or hard templating is a versatile method to produce ordered mesoporous mixed transition metal oxides (MTMOs) with promising potential for both oxygen evolution reaction (OER) and oxygen...

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.

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.

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.

Nano gold-coated surface patterned mesoporous titanium tin oxide sol–gel thin film: fabrication, optical and photoelectrochemical properties

Nano noble metal coating on surface patterned mesoporous semiconductor thin film can play an important role in enhancing visible light harvesting efficiency (LHE) towards improvement in photoelectrochemical (PEC) activity of the material. In this work, one-dimensional (1D) and two-dimensional (2D) mesoscale surface patterns have been created on sol–gel-based titanium tin oxide (TSO) nanostructured thin film on pure silica/indium tin oxide-coated glass by soft lithography. The TSO film matrix is observed to be mesoporous and semicrystalline as evidenced from the structural characterization by transmission electron microscopy and measurement of atmospheric ellipso-porosimetry, respectively. The 2D patterned film exhibits maximum LHE value in visible wavelength region. Further film surface modification has been carried out by depositing nano Au coating onto the bare patterned TSO films by a low temperature solution technique. Under visible light, a significant improvement in PEC activity is found and the gold-coated patterned 2D film shows higher visible LHE as well as >2.7 times higher photocurrent density than bare 2D film. This facile fabrication strategy can create an avenue toward improvement in LHE vis-a-vis the PEC activity of mesoporous mixed metal oxide semiconductor thin film.

Reversible Magnetization Modulation in Ordered Mesoporous Mixed Metal Oxide Thin Films By Double Layer Charging and Topotactic Lithium Insertion

Mesostructured metal oxide thin films have received much attention in recent years. The primary reason for this is the fact that many such materials have been shown to outperform their bulk counterparts. Energy storage and conversion is one of the fields where this is very evident. Advances in polymer templating over the past 10 years have enabled the preparation of various thin film materials with cubic and 2D-hexagonal pore structures and different ordering lenghts.[1] Their formation relies in principle on the coassembly of either sol-gel precursors or preformed building blocks with an amphiphilic polymer structure-directing agent. Despite the progress made so far, complex metal oxides (mixed metal oxides) often exhibit an ill-defined mesoporous morphology after removal of the polymer template and thermally-induced crystallization because of their limited stability. Here, we describe the evaporation-induced self-assembly (EISA)[2] synthesis of cubic mesoporous mixed metal oxide thin films with >15 nm diameter pores and nanocrystalline walls by using a large polyisobutylene-block-poly(ethylene oxide) diblock copolymer. We focus specifically on perovskite-type La1–x Sr x MnO3 (LSMO) and La1–y Ca y MnO3 (LCMO) as well as spinel-type LiFe5O8. These materials were characterized by various state-of-the-art techniques, including electron microscopy, GISAXS, RBS, XRD and XPS, and were found to be of high quality after calcination at elevated temperatures. For LSMO and LCMO, we show that the charge carrier density, and therefore the magnetization, can be modulated through double layer charging (i.e., electrostatic hole- or electron-doping).[3] Magnetization modulation values of up to 10% have been achieved, the highest thus far reported for electrolyte-gated mixed-valence manganese oxides. Apart from that, we show that the room temperature magnetization of LiFe5O8 can be tuned by topotactic insertion/extraction of Li-ions into/from the spinel lattice and provide insights into the mechanism. Both processes allow for control of magnetism, are highly reversible, and strongly benefit from the high surface-to-volume ratio of the films. [1] C. Sanchez, C. Boissiere, D. Grosso, C. Laberty, and L. Nicole, Chem. Mater.20, 682 (2008). [2] C. J. Brinker, Y. F. Lu, A. Sellinger, and H. Y. Fan, Adv. Mater. 11, 579 (1999). [3] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn, and T. Brezesinski, Chem. Mater. 26, 5745 (2014).

Mesoporous In-Sn binary oxides of crystalline framework with extended compositional variation

Indium-tin oxide is considered a highly promising mixed-metal oxide system, because it shows good performance in various industrial processes. Therefore, it will be of great importance to explore the possibility of obtaining new In-Sn oxides with controlled contents whose properties could be tailored. However, In or Sn content in In-Sn oxides has generally been restricted to <10% because of their low solid solubility into counterpart metal oxide framework. Herein, we report for the first solvothermal synthesis of crystalline mesoporous In-Sn oxides with a broad range of In/Sn ratios and their opto-electrochemical properties. For the synthesis, we use phenolic polymer as a structure-directing agent. Surprisingly, we observe that the phenolic polymer plays a critical role in overcoming their low solubility by manipulating kinetics of crystal nucleation and subsequet growth. As a result, we obtain In-rich rutile SnO2 phase without phase separation with up to 50% In content and Sn-rich rhombohedral In2O3 structure with higher In content. The synthesized materials are highly transparent regardless of In content. The electrochemical properties are sensitive to In content. Our strategy offers possibility of realizing crystalline mesoporous mixed-metal oxides with tunable contents, thus opening a new perspective for the development of optoelectronic materials.

Fischer–Tropsch synthesis on the Al2O3-modified ordered mesoporous Co3O4 with an enhanced catalytic activity and stability

Ordered mesoporous Co3O4 metal oxide synthesized by nano-casting method using a hard template of KIT-6 was subsequently modified with Al component to increase catalytic activity and structural stabilities even under H2-rich Fischer–Tropsch synthesis (FTS) conditions. While using a highly ordered mesoporous Co3O4 for FTS reaction, a significant structural change by forming larger cobalt aggregates and encapsulated cokes accelerated a catalyst deactivation. By introducing an irreducible Al species on the inner surfaces or in the main frameworks of mesoporous Co3O4, the ordered mesoporous structures of Co3O4 were successfully maintained even after FTS reaction. These modifications of the mesoporous Co3O4 structures were carried out by adding a pillaring material of aluminum oxide or by preparing mesoporous mixed binary metal oxides with the partial formation of a spinel CoAl2O4 phase, and a higher structural stability and activity were observed due to the suppressed collapses of the mesopore structures of Co3O4. The improved stability of the Co3O4 mesopores seems to be related with a lower mobility of an irreducible Al2O3 pillar by strongly interacting with the inner surfaces of the mesoporous Co3O4 or by enhancing the interactions of Co3O4 with Al2O3 in a main framework of mixed binary metal oxides.

Preparation, characterization, and catalytic activity of Ca2CuO3/CaCu2O3/CaO nanocomposite as a novel and bio-derived mixed metal oxide catalyst in the green synthesis of 2H-indazolo[2,1-b]phthalazine-triones

As a novel and heterogeneous catalyst, the Ca2CuO3/CaCu2O3/CaO nanocomposite was synthesized via coprecipitation and thermal decomposition methods using CuSO4 and eggshell wastes as inexpensive starting materials. The catalytic activity of the mesoporous mixed metal oxide in the synthesis of 2H-indazolo[2,1-b]phthalazine-triones was investigated. The reaction proceeds to completion within 5–20min with yields of 80–94%. The suggested strategy for synthesizing 2H-indazolo[2,1-b]phthalazine-triones is of great interest because a novel, green, and low-cost mixed metal oxide is used as a heterogeneous catalyst, on account of its convenient preparation, short reaction time, and high reusability without any loss of catalytic activity.

Ordered mesoporous mixed metal oxides: remarkable effect of pore size on catalytic activity.

We report the synthesis of ordered mesoporous NiAl mixed metal oxides (MMOs) from NiAl-layered double hydroxides (LDHs) through a soft template method using pluronic-F127 as the structure-directing agent. Ordered mesopores were obtained by the thermal decomposition of as-synthesized LDHs at different temperatures. The effects of the pluronic-F127 amount and the calcination temperature on the pore size distribution of the MMO were investigated. NiAl MMOs exhibited excellent catalytic activity in the Knoevenagel condensation of benzaldehyde with acidic methylene group-containing malononitrile. Finally, the dependence of the catalytic activity on the surface properties of NiAl MMOs was investigated. The pore diameter and the pore volume of NiAl MMOs were well correlated with the performance of the catalysts. MMO obtained from the calcination of NiAl-F127(3%)LDH at 750 °C for 5 h gave the highest conversion (>99%) in the Knoevenagel condensation in 30 min. The optimum pore diameter for the model reaction described here was 7.7 nm, which gave rise to more than 99% conversion with 100% selectivity. Ethanol gave the best conversion at 60 °C. The regenerated catalyst showed 93.0 and 89.0% of the initial catalytic activity after the first and the second regeneration cycles, respectively.

Nanocast mesoporous mixed metal oxides for catalytic applications

Since the initial discovery of ordered mesoporous silica in early 1990s, considerable innovations were achieved regarding their synthesis, characterization and applications. One of the best outcomes of these intense research efforts is the development of a solid templating method called “nanocasting”, which is based on using mesoporous silica (or carbon) as a rigid template. This solid-to-solid replication method opened the pathway for synthesizing high surface area non-silica mesostructured materials that are challenging to obtain through conventional self-assembly processes which are based on amphiphilic soft structure-directing agents. In particular, the replicated metal oxide mesostructures obtained by this method were found to be highly versatile for a wide range of applications, especially in catalysis, owing to their large specific surface area. Furthermore, the nanocasting method is particularly suited for the synthesis of mixed metal compositions, favored by the possible confinement of mixed precursors in the nanopores of the template. In this account, we discuss some of the recent developments regarding the synthesis of nanocast mixed metal oxides and their perspectives of catalytic applications. It is here the choice of the authors to place emphasis on a few representative examples of compositions (e.g., non-noble metal-based catalysts, perovskites) and catalytic reactions (e.g., hydrogen production, gas-phase oxidation). Depuis la découverte de la silice mésoporeuse ordonnée au début des années 1990, des innovations considérables ont été réalisées en ce qui concerne leur synthèse, leur caractérisation et leurs applications. L’un des meilleurs résultats de ces intenses efforts de recherche est le développement d’une méthode de préparation appelée « nano-moulage », qui est basée sur l’utilisation de la silice mésoporeuse (ou de carbone) comme moule. Cette méthode, par réplication solide–solide, a ouvert la voie vers la synthèse de matériaux mésostructurés non siliciques de grande surface spécifique, qui sont difficiles à obtenir par le biais des processus d’autoassemblage moléculaire, basés quant à eux sur l’utilisation d’agents structurants comme les amphiphiles. En particulier, les oxydes métalliques mésostructurés obtenus par cette méthode de réplication peuvent être utilisés dans une large gamme d’applications, en particulier en catalyse, en raison de leur forte surface spécifique. De plus, la méthode de préparation par nano-moulage est particulièrement adaptée à la préparation des oxydes mixtes. La formation d’oxyde mixte est favorisée par le confinement des différents précurseurs des oxydes dans les nanopores de la matrice mésoporeuse. Dans cette revue, nous discuterons les récents développements concernant la préparation d’oxydes métalliques mixtes par la technique de « nano-moulage » et de leurs perspectives d’application en catalyse hétérogène. Le choix des auteurs est ici de mettre l’accent sur quelques exemples représentatifs (par exemple, les catalyseurs à base de métaux non précieux, les pérovskites) et un choix de réactions catalytiques comme la production d’hydrogène ou l’oxydation en phase gazeuse.

Hydrotreating of Heavy Gas Oil on Mesoporous Mixed Metal Oxides (M–Al2O3, M = TiO2, ZrO2, SnO2) Supported NiMo Catalysts: Influence of Surface Acidity

Mesoporous mixed metal oxides, TiO2–Al2O3, ZrO2–Al2O3, and SnO2–Al2O3, were synthesized using a novel method and were used as a support material for the NiMo hydrotreating catalyst. The catalyst was prepared via the incipient wetness sequential impregnation method. All catalysts were characterized using N2 adsorption–desorption isotherms (BET), X-ray diffraction, FTIR, pyridine-FTIR, acridine-FTIR, CO-chemisorption, ICP-MS, TPD, and TPR. The HDS and HDN activities of the catalysts were determined using Athabasca bitumen derived heavy gas oil at industrial reaction conditions. The catalytic activity of synthesized NiMo/γ-Al2O3 catalyst was also determined for comparative studies. Low angle XRD and BET analysis has confirmed that the method developed for synthesis is suitable for the preparation of a mesoporous mixed oxide based NiMo hydrotreating catalyst. H2-TPR analysis has confirmed that the introduction of metal oxides such as ZrO2, TiO2, and SnO2 in alumina increases the active metal (Mo) and support ...

A Generalized Approach to the Synthesis of Mesoporous Mixed Metal Oxides Using the Cation-Anion Double Hydrolysis Method

A series of mesoporous mixed metal oxide were prepared by using a cation-anion double hydrolysis method, which was demonstrated to be a generalized approach for the synthesis of meso-porous mixed metal oxides. The mesoporous mixed oxide were characterized by N adsorption, X-ray diffraction, transmission electronic microscopy and energy dispersive X-ray analysis techniques. Results showed that thus obtained mixed metal oxide catalysts possess a high surface area, high loading of active component together with high dispersion, verifying that this approach is advantageous over the conventional wet impregnation method. The prepared mesoporous mixed oxides exhibit a great potential in replacing the traditional catalysts currently used in many important chemical processes.

Mesoporous mixed metal oxide nanocrystals: Efficient and recyclable heterogeneous catalysts for the synthesis of 1,2-disubstituted benzimidazoles and 2-substituted benzothiazoles

Present communication elicits the use of mesoporous mixed metal oxide nanocrystals of Al 2O 3–Fe 2O 3, Al 2O 3–V 2O 5 and Al 2O 3–CuO as heterogeneous catalysts for the preparation of series of medicinally significant 1,2-disubstituted benzimidazoles and 2-substituted benzothiazoles. These nanocrystalline catalysts exhibited remarkable catalytic activity with a high substrate to catalyst weight ratio (20:1) to achieve the synthetic targets in the range of yield 81–96%. The solvent-free microwave assisted synthesis of these compounds was an advantageous way which resulted in excellent yields in much lesser time (0.75–1.5 min) in comparison to conventional heating. The use of catalyst in eco-friendly green protocol and its reusability up to four cycles with similar catalytic response are the unique features of the heterogeneous catalysis. This protocol provided greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yields.

Hybrid Inorganic−Organic Adsorbents Part 1: Synthesis and Characterization of Mesoporous Zirconium Titanate Frameworks Containing Coordinating Organic Functionalities

A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd<100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and that of the other hybrid phases suggests that the surface-bound ATMP ligand functions as a chelating ligand toward 153Gd3+ under these acidic conditions.

Mesoporous mixed metal oxides derived from P123-templated Mg–Al layered double hydroxides

We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg–Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 °C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg–Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m 2/g, and wide distribution of pore size (2–18 nm). An investigation of the “memory effect” of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers.