Mesoporous Metal Research Articles

Template-free synthesis of mesoporous and amorphous transition metal phosphate materials.

We present how mesoporosity can be engineered in transition metal phosphate (TMPs) materials in a template-free manner. The method involves the transformation of a precursor metal phosphate phase, called M-struvite (NH4MPO4·6H2O, M = Mg2+, Ni2+, Co2+, NixCo1-x2+). It relies on the thermal decomposition of crystalline M-struvite precursors to an amorphous and simultaneously mesoporous phase, which forms during degassing of NH3 and H2O. The temporal evolution of mesoporous frameworks and the response of the metal coordination environment were followed by in situ and ex situ scattering and diffraction, as well as X-ray spectroscopy. Despite sharing the same precursor struvite structure, different amorphous and mesoporous structures were obtained depending on the involved transition metal. We highlight the systematic differences in absolute surface area, pore shape, pore size, and phase transitions depending on the metal cation present in the analogous M-struvites. The amorphous structures of thermally decomposed Mg-, Ni- and NixCo1-x-struvites exhibit high surface areas and pore volumes (240 m2 g-1 and 0.32 cm-3 g-1 for Mg and 90 m2 g-1 and 0.13 cm-3 g-1 for Ni). We propose that the low-cost, environmentally friendly M-struvites could be obtained as recycling products from industrial and agricultural wastewaters. These waste products could be then upcycled into mesoporous TMPs through a simple thermal treatment for further application, for instance in (electro)catalysis.

Electrochemical fabrication of mesoporous metal-alloy films

Electrochemical fabrication integrating templating strategies have paved the way for creating mesoporous metal alloy films with distinctive pores and functionalities for electrocatalysis, fuel cells, and sensor (bio) development.

A new ligand-regulated strategy of highly mesoporous metal–organic framework assembled in ionic liquid/ethanol solvent

The hierarchical porous metal–organic frameworks catalysts were synthesized by ligand regulation in ionic liquid/ethanol system for the first time. The porosity and morphology could be tuned by the mass fraction...

Precisely introducing active sites into NU-1000 through linker incorporation for degrading sulfamethoxazole under visible-light photo-Fenton process

Combining adsorption and catalytic degradation to remove micropollutants in water has become a scientific challenge. However, the current material possessing both suitable pore size and evenly distributed active sites together is less common. Herein, we synthesized stable mesoporous metal–organic framework (MOFs) with Zr6 clusters and carboxylate linkers using solvent-assisted linker incorporation and post-synthetic metalation (NU-1000-Fe). A terpyridine-iron (II/III)-based metal–ligand was introduced into the porous channels successfully in Zr-MOFs without changing the mesoporous skeleton. The remained mesoporosity of the framework facilitated the adsorption of sulfamethylthiazole (SMX) in water (adsorption efficiency ∼ 40 %). Besides, it is verified that efficient p-n heterojunctions were successfully constructed by terpyridine-iron (II/III) and NU-1000. Results show that the accelerated charge transfer and photo-generated electron-hole separation abilities through introducing terpyridine-iron (II/III) facilitate the elimination of SMX in the process of visible-light photo-Fenton (removal efficiency > 90 %). Our findings offer a facile solvent-assisted ligand incorporation strategy for introducing additional active sites into MOFs to promote the degradation of micropollutants in water.

Synthesis of Mesoporous Ag2O/SnO2 Nanospheres for Selective Sensing of Formaldehyde at a Low Working Temperature.

Formaldehyde (HCHO) is a prevalent indoor gas pollutant that has been seriously endangering human health. Developing semiconductor metal oxide (SMO) gas sensors for selective measurement of formaldehyde at low working temperatures remains a great challenge. In this work, silver/tin-polyphenol hybrid spheres are applied as a sacrificial template for the fabrication of spherical mesoporous Ag2O/SnO2 sensing materials. The obtained mesoporous Ag2O/SnO2 spheres have a uniform particle size (∼80 nm), large pore size (5.8 nm), and high specific surface area (71.3 m2 g-1). The response is 140 toward formaldehyde (10 ppm) at a low working temperature (75 °C). The detection limit reaches a low level of 23.6 ppb. Most importantly, it has excellent selectivity toward interfering gases. When the concentration of the interfering gas (e.g., ethanol) is 5 times as high as that of formaldehyde, the response is little affected. Theoretical calculations suggest that the addition of Ag2O can significantly enhance the adsorption energy toward formaldehyde, thus improving formaldehyde sensing performance. This work demonstrates an efficient self-template synthesis strategy for noble metal catalyst-decorated mesoporous metal oxide spheres, which could boost gas sensing performance at a lower working temperature.

Stoichiometric metal nitration based novel green synthesis of mesoporous metal oxides and their enhanced heterogeneity

In this work, a general and novel method for the green synthesis of mesoporous metal oxides via stoichiometric metal nitration has been demonstrated. Pluronic surfactants and their effect on synthesis procedures in terms of surface area have been experimentally studied in detail. Contrary to the traditional synthesis procedure, water has been utilized as the solvent and in several cases, such as tin oxide, manganese oxide, aluminum oxide, antimony oxide, zinc oxide, cobalt oxide, copper oxide, yttrium oxide, lanthanum oxide, and silver either the highest or comparable surface areas have been successfully synthesized. Through XRD, and TEM, all materials were observed to be crystalline except silver and magnesium oxide. SEM shows that with an increase in surfactant molar mass agglomeration decreases. Ammonia chemisorption on acidic materials gives quantitative amounts of ammonia chemical bonding with catalysts, whereas carbon dioxide chemisorption gives a quantitative value of CO2 chemical binding with basic sites. As high as 1901.8 μmol/g and 994.6 μmol/g ammonia chemisorption values for oxides of vanadium and tin were achieved. Amphoteric materials give both acidic and basic enhanced adsorption. Finally, all synthesized materials are studied under organic catalytic transformations. Benzyl bromide is theoretically more active compared with benzylamine and benzyl alcohol which was also experimentally shown through the conversion.

Bifunctional Mesoporous MOx (M = Cr, Fe, Co, Ni, Ce) Oxygen Electrocatalysts for Platinum Group Metal‐Free Oxygen Pumps

A family of crystalline mesoporous metal oxides was synthesized via a soft-templated hydrothermal synthesis route and evaluated as electrocatalysts for oxygen evolution and reduction reactions. The mesoporous NiO was used to elaborate, for the first time, a symmetrical platinum group metal-free oxygen pump. More details can be found in article number 2200927, Zhixing Wu and co-workers.

Tin Oxide (SnO2)-Decorated Reduced Graphene Oxide (rGO)-Based Hydroelectric Cells to Generate Large Current.

Nonphotocatalytic water splitting through oxygen-deficient, mesoporous metal oxide design-based hydroelectric cells (HECs) is a well-known phenomenon. To exploit more power from HECs, a metal oxide with more oxygen deficiency is desirable. In this study, oxygen-deficient mesoporous SnO2 via a sol-gel method and its composites with reduced graphene oxide (rGO) have been presented. Raman spectra of SnO2-rGO nanocomposites revealed an increase in the oxygen vacancies, while the X-ray diffraction (XRD) pattern confirmed the strain formation in the nanocomposite lattice owing to defect formation. The X-ray photoemission spectroscopy (XPS) results also indicated the presence of oxygen vacancies on the surface of SnO2, whereas Brunauer-Emmett-Teller (BET) measurements revealed that adding rGO into SnO2 increased the surface area from 44.54 to 84.00 m2 g-1. The water molecules are chemidissociated on the oxygen-deficient mesoporous surface of the pellet followed by physiodissociation at the mesopores. The redox reaction of the dissociated ions at the Zn anode and the Ag inert cathode produces current in the outer circuit. Interestingly, adding few drops of water into a SnO2-rGO-based HEC resulted in a short-circuit current of 148 mA with an open-cell voltage of 1.0 V. The maximum power delivered by the SnO2-rGO-based HEC is 148 mW. The addition of rGO into SnO2 boosts the peak current remarkably from 68 to 148 mA, which is the highest reported current generated by a hydroelectric cell.

Rare earth Y doping induced lattice strain of mesoporous PtPd nanospheres for alkaline oxygen reduction electrocatalysis

The synthesis of catalysts with controllable morphology and composition is important to enhance the catalytic performance for oxygen reduction reaction (ORR). Herein, trimetallic PtPdY mesoporous nanospheres (PtPdY MNs) are produced via a one-step chemical reduction method applying F127 as soft temple under acidic condition. The mesoporous structure provides a large contact area and also stimulates the diffusion and mass transfer of reactants and products. Besides, synergistic effect among Pt, Pd and Y elements effectively alters their electronic structure, enhancing the catalytic activity. Therefore, the PtPdY MNs show excellent ORR permanence to Pt/C under the alkaline solution. This study offers an effective channel for the preparation of mesoporous metals with rare earth metal doping towards promising electrocatalytic applications.

Functionalization of Mesoporous Semiconductor Metal Oxides for Gas Sensing: Recent Advances and Emerging Challenges.

With the emerging of the Internet of Things, chemiresistive gas sensors have been extensively applied in industrial production, food safety, medical diagnosis, and environment detection, etc. Considerable efforts have been devoted to improving the gas-sensing performance through tailoring the structure, functions, defects and electrical conductivity of sensitive materials. Among the numerous sensitive materials, mesoporous semiconductor metal oxides possess unparalleled properties, including tunable pore size, high specific surface area, abundant metal-oxygen bonds, and rapid mass transfer/diffusion behavior (Knudsen diffusion), which have been regarded as the most potential sensitive materials. Herein, the synthesis strategies for mesoporous metal oxides are overviewed, the classical functionalization techniques of sensitive materials are also systemically summarized as a highlight, including construction of mesoporous structure, regulation of micro-nano structure (i.e., heterojunctions), noble metal sensitization (e.g., Au, Pt, Ag, Pd) and heteroatomic doping (e.g., C, N, Si, S). In addition, the structure-function relationship of sensitive materials has been discussed at molecular-atomic level, especially for the chemical sensitization effect, elucidating the interface adsorption/catalytic mechanism. Moreover, the challenges and perspectives are proposed, which will open a new door for the development of intelligent gas sensor in various applications.

Reticular chemistry for the rational design of mechanically robust mesoporous merged-net metal-organic frameworks

Reticular chemistry for the rational design of mechanically robust mesoporous merged-net metal-organic frameworks

Rapid solid phase microextraction of DNA using mesoporous metal-organic framework coating for PCR-based identification of meat adulteration.

A rapid, convenient, low-cost, and selective DNA isolation method was developed for identifying meat adulteration. A mesoporous metal organic framework (Meso-UIO-66)-coated solid phase microextraction system was employed as an isolation device to simplify DNA isolation into three steps (lysis, washing, and elution). Meso-UIO-66 was utilized as the adsorbent because of its positively charged surface, high chemical stability, and mesoporous structure. Meso-UIO-66 was characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet‒visible spectroscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption tests. Parameters that affected DNA isolation were optimized. This method can be used to isolate and purify DNA from meat in 60s, and the DNA concentration and purity are comparable to those of samples isolated with a commercial kit. Multiple DNA detection was achieved by coupling this method with the multiplex polymerase chain reaction technique, and the detection limit was lower than 1% (w/w).

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.

Efficient separation of methane, ethane and propane on mesoporous metal-organic frameworks

Adsorption and separation of light saturated hydrocarbons (methane, ethane and propane) as main components of natural gas on a series of isoreticular mesoporous metal–organic frameworks NIIC-20-G (G = ethyleneglycol, 1,2-propyleneglycol, 1,2-butyleneglycol, 1,2-pentylenglycol, glycerol) has been thoroughly investigated. An impact of the size and nature of the glycol moiety on fundamental parameters of the adsorption (gas uptakes, adsorption constants, enthalpy and entropy, adsorption selectivity factors) was revealed and rationalized. The highest gas uptakes at 1 bar and 298 K are 13.2 ml(STP)·g−1 for CH4, 55.0 ml(STP)·g−1 for C2H6 and 125.4 ml(STP)·g−1 for C3H8. The IAST adsorption selectivities at ambient conditions (298 K, 1:1 gas mixture) reach 24.2 for C2H6/CH4, 29.0 for C3H8/C2H6 and as high as 1110 for C3H8/CH4. A rare combination of high adsorption uptakes and superb adsorption selectivity values achieved for NIIC-20-G put those MOFs ahead of the most other materials for light saturated hydrocarbon adsorption and separation. Dynamic breakthrough gas separation experiments on NIIC-20-Pr fully confirm effective separation of lighter alkanes from the corresponding binary or ternary mixtures. The obtained methane productivities are 1182 ml(STP)·g−1 (52.8 mol·kg−1) for C2H6/CH4, and 4193 ml(STP)·g−1 (187.3 mol·kg−1) for C3H8/CH4 equimolar gas mixtures, which greatly surpass earlier published data. The ethane productivity for an equimolar C3H8/C2H6 gas mixture is 3009 ml(STP)·g−1 (134.4 mol·kg−1). The breakthrough separation experiments validate a remarkable performance of the studied MOFs in the practical separation of natural gas or other relevant mixtures of light alkanes to valuable individual components.

Bifunctional Mesoporous MOx (M = Cr, Fe, Co, Ni, Ce) Oxygen Electrocatalysts for Platinum Group Metal‐Free Oxygen Pumps

Bifunctional electrocatalysts with both accelerated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) enable high‐power density electricity storage and decentralized extraction of pure oxygen from air for usage in health care. Herein, a hydrothermal synthesis employing the anionic surfactant sodium dodecyl sulfate as structure‐directing agent is developed to fabricate a family of crystalline mesoporous metal oxides (meso‐MO X , M = Cr, Fe, Co, Ni, Ce). The pore size and specific surface area depend on the metal used and they range from 3 to 6 nm and 60 to 200 m2 g−1, respectively. NiO and Co3O4 show a higher catalytic efficiency in alkaline media in comparison with the other oxides studied, and their activities are comparable with the values reported for platinum group metal (PGM)‐based electrocatalysts. This stems from lower voltage losses and by the presence of specific hydroxide adsorbates on the surface. Both ORR and OER driven on Co3O4 show the unified rate‐determining chemical step (|OO−|• ads + H2O ↔ |OOH|• ads + OH−, where are the species adsorbed on active sites). The bifunctional ORR/OER electrocatalysis obtained on mesoporous NiO is utilized for the first symmetrical PGM‐free oxygen pump fed by air and water only.

Bimetallic MOFs-derived core-shell structured mesoporous Sn-doped NiO for conductometric ppb-level xylene gas sensors

Mesoporous metal oxides have proven to be one kind of promising sensitive materials for semiconductor gas sensors that have shown great potential in detection of volatile organic compounds (VOCs) pollutants in air. Here we demonstrate core-shell structured mesoporous Sn-doped NiO derived from the bimetallic metal organic frameworks (MOFs) that synthesized by a combination strategy of hydrothermal and ion-exchange processes for the construction of high-performance xylene gas sensors. The MOFs-derived mesoporous structure can cause the increased amount of sensing reactive sites and improved gas adsorption capacity, as well as provide permeation channel for gas diffusion. In addition, the in-situ substitution of Sn4+ ions for Ni2+ ions can achieve the regulation of charge carrier concentrations. As a consequence, the synthesized core-shell mesoporous 2.64 at% Sn-doped NiO based xylene sensors operating at 250 °C exhibit high sensitivity, excellent selectivity, low detection limit (63 ppb), rapid recovery kinetic and well long-term stability. This work will open up a new pathway toward the development of mesoporous oxides semiconductor gas sensors.

Temperature Effect on Water Adsorption and Desorption Processes in the Mesoporous Metal–Organic Framework MIL-101(Cr)

Mesoporous metal–organic frameworks (MOFs) are potential materials for efficient and reversible water adsorption and desorption processes. However, pore-filling/pore-emptying processes in mesoporous MOFs are complicated due to the complex pore geometry, nonuniform pore surface properties, and polarity of water molecules. In addition, the temperature effects on these processes are still unknown. Here, the temperature effect on the adsorption and desorption processes of water was investigated in a promising mesoporous MOF, namely, MIL-101(Cr). Experimentally measured water adsorption/desorption isotherms show a transition from a one-step to a two-step pore-filling/pore-emptying process with increasing temperature. Theoretical studies revealed that the corresponding mechanism of this transition is related to the relative pressures for the transition between two different stable adsorption states in two different-sized mesopores, the relative pressure at which the inner surface is completely covered with water, and the relative pressure at which condensed water overcomes the energy barrier from the metastable liquid state to the gas state.

Interfacial Catalysis Enabled Acetone Sensors Based on Rationally Designed Mesoporous Metal Oxides with Erbium‐Doped WO3 Framework

AbstractThe emerging combination of Internet of Things requires the development of intelligent gas sensor, and semiconductor gas sensors based on metal oxides have been widely applied in industrial production, environmental monitoring, and food safety. Although versatile nanomaterials have been exploited as gas sensitive materials, restricted gas sensing performance including sensitivity, selectivity and stability, is still the fatal problem of practical applications. Herein, inspired by heteratomic doping engineering, unique rare earth erbium (Er)‐doped mesoporous tungsten oxide (Er/mWO3) has been synthesized via one‐step collaborative coassembly strategy, and Er ion‐doped mWO3 exhibited peculiarly hexagonal mesostructure (P63/mmc), tunable specific surface area (58.1–78.3 m2 g–1), uniform mesoporous size and highly crystallized framework with heteroatomic pore wall doping. The introduction of Er can significantly adjust the micro/nano structure and band characteristics, and 1.5 wt% Er‐doped mWO3 displays superior acetone sensing performance, including high response values (107 for 50 ppm), rapid response–recovery dynamics (9/56 s), prominent acetone selectivity, low concentration detection (125 ppb), anti‐humidity property and excellent long‐term stability. Such an excellent sensing performance is mainly attributed to unique interfaces catalytic sites induced by heteroatom interstitial doping. This finding opens a door for the design of smart gas sensors for environmental monitoring and industrial safety.

Mesoporous copper-based metal glass as current collector for Li metal anode

As functional materials, metal glass (MG) has yet been applied in rechargeable batteries. In this work, we expand their application fields into lithium (Li) metal battery by using them as the current collector for Li anode. To impede the Li dendrites growth during the repeated plating and stripping, we fabricated the CuZr MG ribbon into a genuine mesoporous surface covered with lithiophilic CuOx by a simple dealloying process, which was then used to plate Li metal. The dealloyed CuZr MG current collector with a deposited lithium capacity of 1.0 mAh cm−2 shows a high coulombic efficiency >98 % over 300 cycles at 1.0 mA cm−2. Under a high plating/stripping current density of 2.0 mA cm−2, this Li metal anode shows an ultra-low overpotential of 10 mV after >600 h cycling. Moreover, the full cell coupled with LiFePO4 cathode also displays superior cycling and rate performances. Since the CuZr MG ribbon is industrially produced, this work demonstrates the great potential of MGs for practical application in lithium batteries.

Dual-template synthesis of defect-rich mesoporous Co3O4 for low temperature CO oxidation

CO oxidation is a benchmark in heterogeneous catalysis for evaluation of redox catalysts due to its practical relevance in many applications and the fundamental problems associated with its very high activity at low temperatures. Among which, Co3O4 is one of the most active non-precious metal catalysts. Exposed crystal planes and cobalt sites are considered to be important for its high catalytic activity. Herein, we demonstrate an enhanced CO oxidation activity by a defect-rich mesoporous Co3O4 that prepared by a designed dual-template method. Two different kinds of silicas are used as hard-templates at the same time, resulting in a defect-rich mesoporous Co3O4 with a surface area as high as 169 m2/g. This catalyst exhibited a very high catalytic activity for low temperature CO oxidation with a light-off temperature at −73 oC under the space velocity of 80,000 mL h-1 gcat-1. Further studies reveal that the high surface area promotes the lattice oxygen mobility, surface rich of Co2+ species and active oxygen species are crucial for the high catalytic activity. Moreover, the dual-template approach paves a way towards the design and construction of high-surface-area mesoporous metal oxides for various applications.