Three-dimensional Porous Metal Research Articles

Three-dimensional porous bimetallic metal–organic framework/gelatin aerogels: A readily recyclable peroxymonosulfate activator for efficient and continuous organic dye removal

Three-dimensional porous bimetallic metal–organic framework/gelatin aerogels: A readily recyclable peroxymonosulfate activator for efficient and continuous organic dye removal

Hierarchically porous ZnO derived from zeolitic imidazolate frameworks for high-sensitive MEMS NO2 sensor

Three-dimensional (3D) porous metal oxide nanomaterials with controllable morphology and well-defined pore size have attracted extensive attention in the field of gas sensing. Herein, hierarchically porous ZnO-450 was obtained simply by annealing Zeolitic Imidazolate Frameworks (ZIF-90) microcrystals at an optimal temperature of 450 °C, and the effect of annealing temperature on the formation of porous nanostructure was discussed. Then the as-obtained ZnO-450 was employed as sensing materials to construct a Micro-Electro-Mechanical System (MEMS) gas sensor for detecting NO2. The MEMS sensor based on ZnO-450 displays the excellent gas-sensing performances at a lower working temperature (190 °C), such as high response value (242.18% @ 10 ppm), fast response/recovery time (9/26 s) and ultralow limit of detection (35 ppb). The ZnO-450 sensor shows better sensing performance for NO2 detection than ZnO-based composites materials or commercial ZnO nanoparticles (NPs), which are attributed to its unique hierarchically structures with high porosity and larger surface area. This ZIFs driven strategy can be expected to pave a new pathway for the design of high-performance NO2 sensors.

Numerical Study of Heat and Mass Transfer in the Original Structure and Homogeneous Substitution Model for Three Dimensional Porous Metal Foam

In many applications, such as the miniaturization and cooling of high-power electronics in aerospace, a new thermal management solution is needed, and metal foam radiators may be a valuable solution. In this work, X-ray scanning was applied to obtain the original structure of the metal foam. The real structure calculation model of the metal foam was obtained through a series of modeling, and high-precision numerical simulation was built to study heat and mass transfer in the original structure and homogeneous substitution model for three-dimensional porous metal foam. The distribution of velocity, pressure and temperature field is investigated. The results show that the heat transfer characteristics increase and flow resistance decreases with an increase in the Reynolds number. The heat transfer performance and flow resistance increase with the decrease of porosity. The porous media homogenization model can be consistent with the original real calculation results of metal foam by using appropriate values of resistance coefficient and porosity. The variation of resistance coefficient and porosity with the working condition in the porous homogenization model is identified.

Synthesis, structural characterization, and carbon dioxide and hydrogen adsorption of a new three-dimensional metal organic framework Zn(BTC)4

A novel three-dimensional porous metal organic framework Zn(BTC)4 (BTC = benzene-1,3,5-tricarboxylic acid) is synthesized by the solvothermal method. This structure is characterized by single-crystal X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. This metal organic framework crystallizes in a monoclinic (P2(1)/n, V = 1795.7(2) Å3, Z = 4, Dc = 1.449 mg/cm3, α = 90.00°, β = 97.2200(10)°, γ = 90.00°, a = 9.5077(5) Å, b = 16.3950(16) Å, c = 11.6119(9) Å). The thermogravimetric analysis shows the material can be stabilized up to 350 °C, then the skeleton collapses between 350~510 °C. A luminescence test shows that the material gives out strong emission at 384 and 462 nm. The hydrogen storage capacity of this metal organic framework is 2.01 wt% at 77 K and a pressure of 10 bar. The carbon dioxide storage capacity of this metal organic framework is 4.17 mmol/g at 298 K and a pressure of 10 bar.

General molten-salt route to three-dimensional porous transition metal nitrides as sensitive and stable Raman substrates

Transition metal nitrides have been widely studied due to their high electrical conductivity and excellent chemical stability. However, their preparation traditionally requires harsh conditions because of the ultrahigh activation energy barrier they need to cross in nucleation. Herein, we report three-dimensional porous VN, MoN, WN, and TiN with high surface area and porosity that are prepared by a general and mild molten-salt route. Trace water is found to be a key factor for the formation of these porous transition metal nitrides. The porous transition metal nitrides show hydrophobic surface and can adsorb a series of organic compounds with high capacity. Among them, the porous VN shows strong surface plasmon resonance, high conductivity, and a remarkable photothermal conversion efficiency. As a new type of corrosion- and radiation-resistant surface-enhanced Raman scattering substrate, the porous VN exhibits an ultrasensitive detection limit of 10−11 M for polychlorophenol.

Charge separation in hybrid metal–organic framework films for enhanced catalytic CO2 conversion

A three-dimensional porous metal–organic framework-based hybrid film is prepared through a solid conversion process, demonstrating high photocatalytic performance for CO2 conversion under mild conditions.

Robust Superhydrophobic Composite Featuring Three-Dimensional Porous Metal Rubber with an Embedded Carbon Nanofiber Network for Emulsion Separation

With increasing environmental pollution, super-wetting materials for emulsion separation have attracted considerable attention in recent years. However, there are still major challenges in separati...

Environmentally Friendly, Co-catalyst-Free Chemical Fixation of CO2 at Mild Conditions Using Dual-Walled Nitrogen-Rich Three-Dimensional Porous Metal-Organic Frameworks.

Highly porous, polyhedral metal-organic frameworks (MOFs) of Co(II)/Ni(II), {[M6(TATAB)4(DABCO)3(H2O)3]·12DMF·9H2O} n (where M = Co(II) (1)/Ni(II) (2), H3TATAB = 4,4',4″- s-triazine-1,3,5-triyl-tri- p-aminobenzoic acid, and DABCO = 1,4-diazabicyclo[2.2.2]octane) have been synthesized solvothermally. Both MOFs 1 and 2 show a 2-fold interpenetrated 3D framework structure composed of dual-walled cages of dimension ∼ 30 Å functionalized with a high density of Lewis acidic Co(II)/Ni(II) metal sites and basic -NH- groups. Interestingly, MOF 1 shows selective adsorption of CO2 with high heat of adsorption ( Qst) value of 39.7 kJ/mol that is further supported by theoretical studies with computed binding energy (BE) of 41.17 kJ/mol. The presence of the high density of both Lewis acidic and basic sites make MOFs 1/2 ideal candidate materials to carry out co-catalyst-free cycloaddition of CO2 to epoxides. Consequently, MOFs 1/2 act as excellent recyclable catalysts for cycloaddition of CO2 to epoxides for high-yield synthesis of cyclic carbonates under co-catalyst-free mild conditions of 1 bar of CO2. Further, MOF 1 was recycled for five successive cycles without substantial loss in catalytic activity. Herein, rational design of rare examples of 3D polyhedral MOFs composed of Lewis acidic and basic sites exhibiting efficient co-catalyst-free conversion of CO2 has been demonstrated.

Three-dimensional porous metal electrodes: Fabrication, characterisation and use

Abstract Diverse three-dimensional (3D) porous metal electrodes, including meshes, foams and felts, are used in electrochemical flow reactors for a wide range of industrial applications, such as energy storage, electrosynthesis and degradation of pollutants. Recent work centres on the hierarchical decoration and coating of 3D electrodes with catalysts, although the study of their performance in a controlled and reproducible flow and mass transfer environment ought to receive more attention. New advances have considered metal nanofelts and nanomesh porous electrodes with superior electrode surface area. Opportunities are found in additive manufacturing, advanced structural characterisation by, for example, X-ray computed tomography, and in the modelling of hydrodynamic characteristics, current distribution and mass transfer coefficient of these electrode materials.

Control of Porosity in Parts Produced by a Direct Laser Melting Process

Recent advances in direct laser melting (DLM) have demonstrated its great potential for manufacturing three-dimensional porous metal parts. Various combinations of powder layering and processing parameters can be set to adjust the porous properties of the final parts. This study presents the effects of powder morphologies and process parameters on porosity formation during DLM. Four types of Fe-powders composed of spherical or non-spherical particles with different sizes were experimentally investigated. Furthermore, the laser processing parameters, such as laser energy density, laser focus, and line spacing, which have a significant effect on the results, were characterized. In the case of a mixed powder composed of spherical and non-spherical powders, the packing density decreases as the non-spherical powder size increases. The porosity of the laser-melted layer increases with the degree of size misfit between the non-spherical and spherical powders. Decreased laser absorption and enlargement of the powder-depleted zone as a result of decreased packing density increases the porosity during DLM. The overall results show that the porosity of DLM parts could be actively controlled by adjusting the process parameters and powder morphologies.

Photochromic Porous and Nonporous Viologen-Based Metal–Organic Frameworks for Visually Detecting Oxygen

The detection of the oxygen molecule is of particular interest due to various applications in chemical, biological, and environmental areas, and the typical materials of detecting O2 such as Clark-type electodes and optical oxygen sensors suffer from disadvantages such as insensitivity or usage of expensive instrument. In this paper, we present a nonporous two-dimensional viologen-based metal–organic frameworks consisting of pseudo-left- and right-handed helical chains [Cd(CPBPY)(o-BDC)(H2O)]·H2O (CPBPY = N-(3-carboxyphenyl)-4,4′-bipyridinium, o-BDC = o-benzenedicarboxylate) (1) that exhibits a slow photochromism under a vacuum, inert atmosphere, and even exposure to oxygen, and a three-dimensional porous 6-connected pcu topological metal–organic framework [Cd3(CPBPY)2(BDC)3]·DMF·H2O (BDC = 1,4-benzenedicarboxylate) (2), which displays rapid photochromism only under a vacuum or inert atmosphere. The photochromic product 2′ can quickly and conveniently detect O2 by naked eye recognition of color change. Th...

Theoretical investigation of selective catalytic reduction of NO on MIL-100-Fe.

MIL-100-Fe, a three-dimensional porous metal organic framework material, shows good activity for the selective catalytic reduction of NO by ammonia. Understanding reaction mechanisms at the molecular level contributes to the design and development of highly active catalysts. Herein, density functional theory calculations with the consideration of van der Waals interactions were performed to investigate the SCR mechanism on MIL-100-Fe. Lewis acid sites and Brønsted acid sites both exist on MIL-100-Fe, which are active for the SCR reaction. MIL-100-Fe exhibits the features of single-site catalysts, thus we calculated the NH3-SCR reaction process following the Eley-Rideal mechanism. The proposed NH3-SCR mechanism can be subdivided into two parts: (1) NO oxidation and (2) fast SCR reaction. Our results show that Lewis acid sites play an essential role in activating the reactants. The NO molecule is readily oxidized to NO2 species on the Fe Lewis acid sites, the adsorbed NH3 species react with gaseous NO2, and the formation of intermediate NH2NO is the rate-determining step. This study offers new and important insights into the mechanistic understanding of the NH3-SCR reaction on the MIL-100-Fe catalyst.

A novel fabrication approach for three-dimensional hierarchical porous metal oxide/carbon nanocomposites for enhanced solar photocatalytic performance

A novel approach for the fabrication of metal oxide/C composites with a hierarchical porous structure is proposed.

Facile Synthesis of Three-Dimensional Pt-TiO2 Nano-networks: A Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia-Borane.

Three-dimensional (3D) porous metal and metal oxide nanostructures have received considerable interest because organization of inorganic materials into 3D nanomaterials holds extraordinary properties such as low density, high porosity, and high surface area. Supramolecular self-assembled peptide nanostructures were exploited as an organic template for catalytic 3D Pt-TiO2 nano-network fabrication. A 3D peptide nanofiber aerogel was conformally coated with TiO2 by atomic layer deposition (ALD) with angstrom-level thickness precision. The 3D peptide-TiO2 nano-network was further decorated with highly monodisperse Pt nanoparticles by using ozone-assisted ALD. The 3D TiO2 nano-network decorated with Pt nanoparticles shows superior catalytic activity in hydrolysis of ammonia-borane, generating three equivalents of H2 .

Structure-versus-luminescence reversibility and solvent adsorption properties of a three-dimensional porous supramolecular metal–organic framework studied by synchrotron X-ray powder diffraction

Structure-versus-luminescence reversibility and solvent adsorption properties of a three-dimensional porous supramolecular metal–organic framework studied by synchrotron X-ray powder diffraction

Three-dimensional porous metal–nitrogen doped carbon nanostructure as a superior non-precious electrocatalyst in oxygen reduction reaction

We report the porous transition metal–nitrogen doped carbon nanostructures as cathode catalysts using a well-stacked arrangement of template materials in the presence of polyvinylpyrrolidone as nitrogen and carbon sources and metal phthalocyanine as metal and nitrogen sources. The as-prepared nanostructures show high specific surface areas (105.73–228.13m2g−1), porous structure, and doped metal and nitrogen species (pyridinic-N, pyrrolic-N, and graphitic-N) into carbon structures. In particular, the porous Fe–N-doped carbon nanostructure exhibits excellent ORR electrocatalytic properties in alkaline electrolyte; i.e., electron transfer number close to 4, high half-wave potential (0.81V), improved electrochemical stability (a slight decrease of ∼31mV in the half-wave potential after the stability test), and methanol tolerance.

General Preparation of Three-Dimensional Porous Metal Oxide Foams Coated with Nitrogen-Doped Carbon for Enhanced Lithium Storage.

Porous metal oxide architectures coated with a thin layer of carbon are attractive materials for energy storage applications. Here, a series of porous metal oxide (e.g., vanadium oxides, molybdenum oxides, manganese oxides) foams with/without nitrogen-doped carbon (N-C) coating have been synthesized via a general surfactant-assisted template method, involving the formation of porous metal oxides coated with 1-hexadecylamine (HDA) and a subsequent thermal treatment. The presence of HDA is of importance for the formation of a porous structure, and the successive pyrolysis of such a nitrogen-containing surfactant generates nitrogen-doped carbon (N-C) coated on the surface of metal oxides, which also provides a facile way to adjust the valence states of metal oxides via the carbothermal reduction reaction. When used as electrode materials, the highly porous metal oxides with N-C coating exhibited enhanced performance for lithium ion storage, thanks to the unique 3D structures associated with highly porous structure and thin N-C coating. Typically, the porous metal oxides (V2O5, MoO3, MnO2) exhibited discharge capacities of 286, 303, and 463 mAh g(-1) at current densities of 30 and 100 mA g(-1), respectively. In contrast, the metal oxides with low valences and carbon coating (VO2@N-C, MoO2@N-C, and MnO@N-C) exhibited improved capacities of 461, 613, and 892 mAh g(-1). The capacity retentions of about 87.5, 80.2, and 85.0% for VO2@N-C, MoO2@N-C, and MnO@N-C were achieved after 600 cycles, suggesting the acceptable cycling stability. The present strategy would provide general guidance for preparing porous metal oxide foams with enhanced lithium storage performances.

Gold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces.

Three-dimensional (3D) porous metal nanostructures have been a long sought-after class of materials due to their collective properties and widespread applications. In this study, we report on a facile and versatile strategy for the formation of Au hydrogel networks involving the dopamine-induced 3D assembly of Au nanoparticles. Following supercritical drying, the resulting Au aerogels exhibit high surface areas and porosity. They are all composed of porous nanowire networks reflecting in their diameters those of the original particles (5–6 nm) via electron microscopy. Furthermore, electrocatalytic tests were carried out in the oxidation of some small molecules with Au aerogels tailored by different functional groups. The beta-cyclodextrin-modified Au aerogel, with a host–guest effect, represents a unique class of porous metal materials of considerable interest and promising applications for electrocatalysis.

Control of interpenetration in a microporous metal-organic framework for significantly enhanced C2H2/CO2 separation at room temperature.

A novel non-interpenetrated three-dimensional porous metal-organic framework UTSA-68 has been controllably synthesized by altering the reaction conditions. The resulting UTSA-68a shows a notably higher porosity and adsorption selectivity (3.5-5) for C2H2/CO2 separation compared to that of doubly interpenetrated ZJU-30a (1.7-2.4) at room temperature.

A three-dimensional porous metal foam with selective-wettability for oil–water separation

The development of selective-wettability surfaces of porous materials is important for oil spill cleanup. A new type of oil–water separation material has been prepared through a three-dimensional (3-D) extension of a biologically inspired two-dimensional (2-D) material. In this, a simple solution-immersion method is used to construct a super-oleophilic and super-hydrophobic surface on the metallic skeleton of a copper foam, onto which a nanosheet structure is formed that differs greatly from previous nanoscale needle-based materials. This 3-D copper foam is demonstrated to be capable of supporting a maximum height of accumulated water of 5.5 cm prior to oil wetting and 1.5 cm after oil wetting. Furthermore, the foam is capable of efficient oil–water separation, despite losing its super-hydrophobicity during the process. This has given important new insight into the mechanism of separation, in that super-oleophilicity is clearly important to achieving good separation. The selective-wettability of this porous metal foam is expected to extend the range of metal-based oil–water separation materials from 2D metal meshes to more complex 3-D metal structures.