Hollow Metal Research Articles

Preparation of novel hollow metal organic framework for enhancing flame retardancy of paraffin/EP thermal energy storage materials

AbstractParaffin is a potential thermal energy storage material, but leakage and flammability are the two major problems affecting its storage and safe use. Here, a novel flame retarded paraffin/epoxy resin composite was developed by using paraffin, epoxy resin and hollow metal organic framework (W‐UiO66‐PPA) as thermal energy storage material, supporting material and flame retardant, respectively. The thermal energy storage and flame retardancy performances were examined with differential scanning calorimetry, vertical burning, limiting oxygen index and cone calorimeter tests. The results show that the paraffin/epoxy resin retains intact without leakage when the content of paraffin reaches 40 wt%, and this material exhibits high melting latent heat and remarkable thermal recycling property. In addition, the flame retarded paraffin/epoxy resin shows excellent flame retardancy, which is attributed to the following three aspects: (1) the hollow structure with open vertices of W‐UiO66 is capable of absorbing and collecting the combustible gasses produced by the combustion of epoxy resin; (2) the Zr and W elements of W‐UiO66 can facilitate catalytic charring and form a dense char layer; (3) phosphorous‐containing free radicals are able to capture OH· and O· free radicals during the combustion of paraffin and epoxy resin, thus interrupting the combustion chain reaction. On the whole, the flame retarded paraffin/EP possesses excellent thermal energy storage, thermal recycling, and flame retardancy properties. Our work provides a fantastic inspiration for the rational design of other flame retarded form‐stable phase change materials.

Integration of Noble Metal Nanocrystals in a Hollow Metal–Organic Framework Shell

Integration of Noble Metal Nanocrystals in a Hollow Metal–Organic Framework Shell

Enhanced Electrochemical Sensing of Butylated Hydroxy Anisole through Hollow Metal–Organic Frameworks with Gold Nanoparticles and Enzymes

Enhanced Electrochemical Sensing of Butylated Hydroxy Anisole through Hollow Metal–Organic Frameworks with Gold Nanoparticles and Enzymes

High performance Hetero-Shelled hollow structure Metal-Organic framework hybrid material for the efficient electrochemical determination of lead ions

Electrochemical sensing has unique advantages in developing on-site and online detection technologies for heavy metal ions (HMIs) due to its fast response, simple operation, high sensitivity, and portable instruments. The vigorous development of modern micro/nanomaterial preparation technology has provided greater space for improving the performance of electrochemical sensing platforms. In this work, a novel hetero-shelled hollow structure metal–organic framework (MOF) hybrid material (denoted as HCZ@UN) was prepared by adopting the hollow carbonized ZIF-8 (HCZ) as the substrate for growing UiO-66(Zr)–NH2 (UN), and subsequently used for efficient electrochemical detection of lead ions (Pb2+). The grown UN crystal particles were anchored on the HCZ hollow cages and showed nanometer size. The unique shell structure and nanometer size of UN created large specific surface area and rich accessible adsorption sites, which promoted the preconcentration of Pb2+. While the hollow carbon polyhedron structure of HCZ improved the dispersibility of UN and electron transfer ability of the material. These factors synergistically improved the detection sensitivity and sensing performance for Pb2+ determination with a wide linear range of 0.100–500 nM, a low detection limit of 0.0492 ± 0.00523 nM as well as good selectivity, repeatability and long-term stability. This paper provides a simple and effective method for the preparation of electroactive MOF functional materials, which is expected to inspire more interest in building other MOF-based materials with unique structure, high-performance and extensive application value.

РАЗРАБОТКА ЛИТЕЙНОЙ ТЕХНОЛОГИИ ПОЛУЧЕНИЯ ПОРИСТОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА НА ОСНОВЕ АЛЮМИНИЯ

The work is devoted to the development of technology for obtaining composite material based on aluminium alloy with a given morphology of pores by using hollow metal spheres as pore formers. In the course of work the following researches have been carried out: selection of material-former of hollow metal spheres forming the structure and physical and mechanical properties of porous aluminum; study of influence of binder type on uniformity of conductive coating on the surface of form-former; study of influence of electrolysis modes on continuity of metal coating on the surface of conductive layer of formformer; production of porous aluminum by foundry technology. It is shown that the use of hollow metallized spheres as a pore former allowed to reduce the density of the AK12 alloy prototype by 40%.

Construction of hollow binary oxide heterostructures by Ostwald ripening for superior photoelectrochemical removal of reactive brilliant blue KNR dye

Although the Ostwald ripening approach is often utilized to manufacture single hollow metal oxide, constructing hollow binary oxide heterostructures as potent photoelectrochemical (PEC) catalysts is still obscure and challenging. Herein, we reveal a general strategy for fabricating hollow binary oxides heterostructures (Co3O4-δ-MnO2 and Co3O4–SnO2) utilizing Ostwald ripening. Hollow Co3O4-δ-MnO2 nano-network with the structure evolution process was systematically explored through experimental and theoretical tools, identifying the origin of hollow binary oxides due to the interfaces acting as landing sites for their growth. In addition, the structural evolution, from hollow Co3O4-δ-MnO2 to Co3O4-α-MnO2, can be observed when the time of secondary hydrothermal reaches 96 ​h due to the topotactic layer-to-tunnel transition process. Notably, optimized Co3O4-δ-MnO2-48 exhibits a superior PEC degradation efficiency of 96.42% and excellent durability (20,000 ​min) under harsh acid conditions, attributed to the massive hollow structures' vast surface area for high intently active species. Furthermore, density functional theory simulations elucidated the Co3O4-δ-MnO2’ electron-deficient surface and high d-band center (Co3O4-δ-MnO2, -1.06; Co3O4-α-MnO2, -1.49), strengthening the interaction between the catalyst's surface and active species and prolonging the lifetime of active species of •O2− and 1O2. This work not only demonstrates superior PEC degradation efficiency of hollow Co3O4-δ-MnO2 for practical use but also lays the cornerstone for constructing hollow binary oxides heterostructures through Ostwald ripening.

Carbonizing hollow metal–organic framework/layered double hydroxide (MOF/LDH) nanocomposite with excellent adsorption capacity for removal of Pb(II) and organic dyes from wastewater

A novel sorbent ZIF-67/LDH@C was synthesised using mild etching and co-precipitation and carbonization calcination for the elimination of lead ions (Pb2+), malachite green (MG), and congo red (CR) from water. The three-dimensional hollow MOF structure and two-dimensional LDH nanosized layers of ZIF-67/LDH@C were demonstrated by scanning electron microscope (SEM), transmission electron microscopy (TEM), fourier transform infrared (FT-IR), X-ray diffraction (XRD), nitrogen adsorption/desorption, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) characterization. The maximal adsorption capability of Pb2+, MG, and CR could reach 662.25, 1729.83 and 526.32 mg∙g−1, respectively. The kinetic study proved that the adsorption was chemisorption or strong complexation and the rate-limiting step was intraparticle diffusion. The isotherms effectively indicated the monomolecular-type adsorption. Thermodynamic studies showed the spontaneous and endothermic nature of Pb2+, MG and CR adsorption onto ZIF-67/LDH@C. The adsorption mechanisms of ZIF-67/LDH@C may be attributed to electrostatic attraction, π-π interaction, hydrogen-bonding interaction, and surface complexation between ZIF-67/LDH@C and pollutants. Furthermore, favourable stability and negligible interference from other metal ions could promote the viability of the practical application of ZIF-67/LDH@C in wastewater purification.Graphical

Promoting High-Oxidation-State Metal Active Sites in a Hollow Ternary Metal Fluoride Nanoflake Array for Urea Electrolysis.

The adsorption ability of hydrogen, hydroxide, and oxygenic intermediates plays a crucial role in electrochemical water splitting. Electron-deficient metal-active sites can prompt electrocatalytic activity by improving the adsorption ability of intermediates. However, it remains a significant challenge to synthesize highly abundant and stable electron-deficient metal-active site electrocatalysts. Herein, we present a general approach to synthesizing a hollow ternary metal fluoride (FeCoNiF2) nanoflake array as an efficient and robust bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). We find that the F anion withdraws electrons from the metal centers, inducing an electron-deficient metal center catalyst. The rationally designed hollow nanoflake array exhibits the overpotential of 30 mV for HER and 130 mV for UOR at a current density of 10 mA cm-2 and superior stability without decay events over 150 h at a large current density of up to 100 mA cm-2. Remarkably, the assembled urea electrolyzer using a bifunctional hollow FeCoNiF2 nanoflake array catalyst requires cell voltages of only 1.352 and 1.703 V to afford current densities of 10 and 100 mA cm-2, respectively, which are 116 mV less compared with that required for overall water splitting.

Development of a resonant screw-driven piezoelectric motor operating in single-mode vibration.

A resonant screw-driven piezoelectric motor operating in single-mode vibrations is proposed, designed, manufactured, and studied. The motor is constructed with a stator and a threaded rotor. The stator consists of a hollow parallelogram metal elastomer and two piezoelectric ceramic plates. The motor is excited by a single-phase signal to produce two separate vibration modes: the first expansion mode (B1 mode) and the second expansion mode (B2 mode). Each mode drives the threaded rotor in one direction, and the bidirectional motion is achieved by switching the two modes. The construction is designed, and modal simulation is performed using finite element software to determine the structural parameters. A frequency-domain analysis is performed to obtain the frequency response characteristics, and the motion trajectories of the stator are obtained using transient analysis. Finally, a prototype is produced, and experiments are conducted. Experimental results indicate that the no-load speeds of the motor under the 200 Vp-p voltage excitation are 1.67 and 1.04 mm/s in the two modes, which correspond to maximum loads of 35 and 20mN, respectively.

Engineering sensitive gas sensor based on MOF-derived hollow metal-oxide semiconductor heterostructures

Metal-organic frameworks (MOFs) derived hollow heterostructured metal oxide semiconductors (MOSs) are a class of functional porous materials exhibiting distinctive physiochemical properties. Owing to the unique advantages, including large specific surface, high intrinsic catalytic performance, abundant channels for facilitating electron transfer and mass transport, and strong synergistic effect between different components, MOF-derived hollow MOSs heterostructures can work as promising candidates for gas sensing, which have thus attracted increasing attention. Aiming to provide a deep understanding on the design strategy and MOSs heterostructure, this review presents a comprehensive overview on the advantages and applications of MOF-derived hollow MOSs heterostructures when they used n for the detection of toxic gases. In addition, a deep discussion about the perspective and challenge of this interesting field is also well organized, hoping to provide guidance for the future design and development of more accurate gas sensors.

Hollow Mesoporous Metal Organic Framework Single Crystals Enabled by Growth Kinetics Control for Enhanced Photocatalysis

AbstractThe tailored design of hollow mesoporous metal−organic framework (MOF) single crystals to realize the unimpeded mass transport and long‐range carrier migration for advanced photoelectric applications is attractive while being a major challenge. Here, a kinetically mediated micelle assembly strategy is presented to synthesize hollow UiO‐66(Ce) single crystals in 1,3,5‐trimethylbenzene (TMB)‐H2O emulsion system with Pluronic F127/P123 as dual surfactants. This synthesis features the employment of modulator acetic acid, which can coordinate growth kinetics of MOFs, allowing the nucleation of MOF on block polymer micelles and transforming the self‐assembly of block polymer/MOF composite monomicelles from water to TMB/H2O emulsion interface and the growth of MOF from aggregation to oriented attachment, and thus ensuring the formation of hollow mesoporous UiO‐66(Ce) single crystals. Moreover, a precise control in cavity diameter from ≈0 to ≈600 nm, mesopore structure from close to radial and dendritic can be achieved by tuning the amount of TMB and the ratio of F127/P123. As a result, the hollow mesoporous UiO‐66(Ce) single crystals with large radial mesopores (≈25 nm) and high surface area (≈1061 m2 g) exhibit excellent photocatalytic performance for H2 generation owing to enhanced permeability and suppressed electron‐hole combination.

PH-responsive dual-enzyme mimics based on hollow metal organic framework-derivatives β-Co(OH)2 for multiple colorimetric assays.

Ahollow metal organic framework derivative β-Co(OH)2has been prepared, which possesses oxidase and peroxidase-like activities. Oxidase-like activity is derived from the generation of free radicals, and peroxidase-like activity is related to the electron transfer process. Unlike other nanozymes with dual enzyme-like activities, β-Co(OH)2 possesses pH-responsive enzyme-like activities, among which the β-Co(OH)2 exhibits superior oxidase and peroxidase-like activities under pH of 4 and 6, respectively, which could avoid mutual interference between multiple enzymes. Based on the phenomenon that enzyme-like activities of β-Co(OH)2 can catalyze colorless TMB to generate blue oxidized TMB (oxTMB) with absorption peak at 652 nm, the sensors integrating total antioxidant capacity and H2O2 quantification were developed. The oxidase-like activity-based colorimetric system has a sensitive response to ascorbic acid, Trolox, and gallic acid, in which the limit of detection for those antioxidant substances was 0.54 μM, 1.26 μM, and 14.34 μM, respectively. The sensors based on peroxidase-like activity hadlow limit of detection of 1.42 μM for H2O2 and alinear range of 5-1000 μM. Theproposed method can be well applied to the detection of the total antioxidant capacity of kiwi, Vc tables, orange and tea extract with high accuracy, and H2O2 determination in milk and glucose detection in beverages with satisfactory recovery (within 97-106%).

Preserving Macroporosity in Type III Porous Liquids

AbstractPreserving large permanent pore structures in a fluid may endow conventional liquids with emergent physical properties. However, such materials are challenging to make because of the tendency of the pores to be filled and occupied by the solvent molecules. Here, we report the design and synthesis of the first Type III porous liquid (PL) containing uniform yet stable 480 nm cavities. This was achieved by first constructing a single crystalline hollow metal–organic framework (MOF), UiO‐66‐NH2, through chemical etching. The thin yet defect‐free MOF shell effectively excludes the bulky poly(dimethylsiloxane) solvent molecules from entering the cavity through its 4 Å aperture, resulting in the preservation of both micro‐ and macroporosity in the PL. These enormous void spaces allow the PL to reversibly host and release up to 27 wt % water for up to 10 cycles. The switching between the “dry” state and the “wet” state led to a large changes of the thermal conductivity of the PL from 0.140 to 0.256 W m−1 K−1, affording a guest‐responsive liquid thermal switch with a switching ratio of 1.8.

Triple-shelled nickel-cobalt-manganese sulfides hollow spheres for advanced hybrid supercapacitors

To design high-performance hybrid supercapacitors, positive and negative electrode materials with superior electrochemical features are needed. This paper proposes the fabrication of a hybrid supercapacitor using hollow ternary mixed metal sulfides as a positive electrode and iron oxide-decorated nitrogen-doped reduced graphene oxide (Fe3O4/N-rGO) as the negative electrode. Triple-shelled hollow spheres of nickel-cobalt-manganese-sulfides (NCMS) are synthesized using an optimum calcination temperature, followed by post-sulfurization. As the positive electrode, NCMS produced at 350 °C (NCMS-350) displays a high specific capacity of 797 C g−1 (1885 F g−1) at 1 A g−1 with excellent rate capability (79.5% at 20 A g−1). On the other hand, the negative Fe3O4/N-rGO electrode is synthesized hydrothermally without post-calcination and exhibits a maximum specific capacity of 454 C g−1 (378 F g−1) at 1 A g−1. Moreover, the NCMS-350//Fe3O4/N-rGO hybrid device delivers an impressive energy density of 67.9 Wh kg−1 at 474 W kg−1. These promising electrochemical performances provide a facile strategy for optimizing and integrating electrode materials to develop high-performance hybrid supercapacitors for efficient energy storage.

Preparation of Single-Ni atom active points by anchoring Anderson polyoxometalate in HKUST-1 for efficient Symmetric/ Asymmetric device energy storage and electrocatalytic overall water splitting

We explore and synthesize hollow polyoxometalate-based metal–organic framework (POMOF) nanomaterial {Cu(NH4)2NiMo6O24H6}@HKUST-1 (HRBNU-2) with single-atom sites (SASs) by one-step solution method. It exhibits high specific capacitance (978.50F g−1) in neutral electrolyte. Symmetrical/Asymmetrical devices can light four Red Light Emitting Diodes (RLEDs)/one RLED on for 14 min. For electrocatalytic water splitting, the overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline medium are 192.98 mV (η100) and 405.38 mV (η100). The double-layer capacitance (Cdl) of HRBNU-2 is 269.23 mF cm−2, reaching about 4.43 times of {Cu2(NH4)2Mo7O24}@HKUST-1 (HRBNU-3) and about 12.70 times of HKUST-1. Moreover, the device assembled by HRBNU-2 as cathode and anode, requires only 1.61 V cell voltage to achieve current density of 10 mA cm−2 and obtain stability of 100 h. Meanwhile, comparative study of HRBNU-3 system with similar structural composition is synthesized to illustrate that the synergy of SASs(Ni) and Mo in well-defined structures plays important role in the study of efficient overall water splitting and supercapacitance performance.

Hollow Core-Shell Metal Oxide Heterojunctions for the Urinary Metabolic Fingerprint-Based Noninvasive Diagnostic Strategy.

Urine is a preferred object for noninvasive diagnostic strategies. Urinary metabolic analysis is speculatively regarded as an ideal tool for screening diseases closely related to the genitourinary system in view of the intimate relationship between metabolomics and phenotype. Herein, we propose a urinary metabolic fingerprint-based noninvasive diagnostic strategy by designing hollow core-shell metal oxide heterojunctions (denoted as MOHs). With outstanding light absorption and electron-hole separation ability, MOHs aid in the extraction of high-performance urine metabolic fingerprints. Coupled with optimized machine learning algorithms, we establish a metabolic marker panel for accurate diagnosis of prostate cancer (PCa), which is the most common malignant tumor of the male genitourinary system, achieving accuracies of 84.72 and 83.33% in the discovery and validation sets, respectively. Furthermore, metabolite variations and related pathway analyses confirm the credibility and change correlation of key metabolic features in PCa. This work tends to advance the noninvasive diagnostic strategy toward clinical realities.

Electrochemiluminescence Immunosensors Based on ECL-RET Triggering between Mn SANE/PEI-Luminol and PtCu/h-MPF for Ultrasensitive Detection of CEA.

In this paper, a novel donor-acceptor pair was creatively proposed based on the principle of electrochemiluminescence resonance energy transfer (ECL-RET): luminol immobilized on polyethyleneimine (PEI)-functionalized manganese-based single-atom nanozymes (Mn SANE/PEI-luminol, donor) and a PtCu-grafted hollow metal polydopamine framework (PtCu/h-MPF, acceptor). A quenched ECL immunosensor was constructed for the ultrasensitive analysis of carcinoembryonic antigen (CEA). Mn SANE, as an efficient novel coreaction accelerator with the outstanding performance of significantly activating H2O2 to produce large amounts of ROS, was further modified by the coreactant PEI, which efficiently immobilized luminol to form a self-enhanced emitter. As a result, the electron transport distance was effectively shortened, the energy loss was reduced, and luminol achieved a high ECL efficiency. More importantly, PtCu-grafted h-MPF (PtCu/h-MPF) was proposed as a novel quencher. The UV-vis spectra of PtCu/h-MPF partially overlap with the ECL spectra of Mn SANE/PEI-luminol, which can effectively trigger the ECL-RET behavior between the donor and the acceptor. The multiple quenching effect on Mn SANE/PEI-luminol was achieved, which significantly improved the sensitivity of the immunosensor. The prepared immunosensor exhibited good linearity in the concentration range of 10-5 to 80 ng/mL. The results indicate that this work provides a new method for the early detection of CEA in clinical diagnosis.

Coordinated Immobilization and Rapid Conversion of Polysulfide Enabled by a Hollow Metal Oxide/Sulfide/Nitrogen-Doped Carbon Heterostructure for Long-Cycle-Life Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are recognized as the prospective candidate in next-generation energy storage devices due to their gratifying theoretical energy density. Nonetheless, they still face the challenges of the practical application including low utilization of sulfur and poor cycling life derived from shuttle effect of lithium polysulfides (LiPSs). Herein, a hollow polyhedron with heterogeneous CoO/Co9 S8 /nitrogen-doped carbon (CoO/Co9 S8 /NC) is obtained through employing zeolitic imidazolate framework as precursor. The heterogeneous CoO/Co9 S8 /NC balances the redox kinetics of Co9 S8 with chemical adsorption of CoO toward LiPSs, effectively inhibiting the shuttle of LiPSs. The mechanisms are verified by both experiment and density functional theory calculation. Meanwhile, the hollow structure acts as a sulfur storage chamber, which mitigates the volumetric expansion of sulfur and maximizes the utilization of sulfur. Benefiting from the above advantages, lithium-sulfur battery with S-CoO/Co9 S8 /NC achieves a high initial discharge capacity (1470 mAh g-1 ) at 0.1 C and long cycle life (ultralow capacity attenuation of 0.033% per cycle after 1000 cycles at 1 C). Even under high sulfur loading of 3.0 mg cm-2 , lithium-sulfur battery still shows the satisfactory electrochemical performance. This work may provide an idea to elevate the electrochemical performance of LSBs by constructing a hollow metal oxide/sulfide/nitrogen-doped carbon heterogeneous structure.

Emission control using Carbon Silencer

: For the purpose of mitigating emission and noise in an automotive exhaust system, a carbon silencer is utilized. It is assembled using a perforated hollow metal tube, external casing, activated charcoal and a solution of limestone. The engine's exhaust pipe is connected to the carbon silencer. The hazardous sulfur oxides and nitrogen oxides elements generated by the engine are filtered by activated charcoal. Compared to sound produced in a traditional silencer, sound produced within limestone water is less audible. This is primarily due to little sprockets in water molecules, which reduces its amplitude and hence the sound level. Due to the presence of activated charcoal which has more surface area than regular charcoal it is known as Carbon Silencer. When tested in a single cylinder 4-stroke petrol engine, the noise and smoke levels are significantly lower compared to a typical silencer. Automobiles contribute the majority of pollutants, which include carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), and lead. Other sources include electric power plants, industrial and household fuel usage, trash burning, and industrial processes. Carbon silencers are used to decrease emissions and noise

An advanced method for predicting the axial compressive bearing capacity of fiber-reinforced polymer-strengthened hollow section metal columns

Successful experimental and theoretical studies have promoted fiber-reinforced polymer (FRP) as an innovative strengthening material for metal columns in structural engineering, highlighting the necessity for an effective and reliable calculation method for such strengthened members. Here, based on existing experimental data, an advanced method using an artificial neural network (ANN) is developed to predict the axial compression bearing capacity (ACBC) of FRP-strengthened hollow section metal (FSHM) columns, where FRP strengthening includes wrapping/bonding FRP sheets/laminates; this method considers realistic conditions, incorporates a variety of parameters, and produces accurate and fast predictions. First, a multilayer perceptron (MLP) neural network was applied. By studying the optimization algorithm, learning rate, hidden vector and activation function, an optimal ANN model was established, which yielded better predictive accuracies and safety than existing calculation methods. Using the validated model, an prediction program was developed that promptly generated predictions of ACBC with a high reliability. Finally, a sensitivity analysis was performed to further assess the effects of key parameters on the behavior of FSHM columns to provide practical recommendations for their design.