Metal-organic Framework Derivatives Research Articles

Facile synthesis of CoFe/C nanoparticle embedded in nitrogen and sulfur co-doped reduced graphene oxide nanocomposites for electromagnetic wave absorption

Three-dimensional metal–organic framework derivatives (MOFs) offer significant potential for the absorption of electromagnetic waves (EMW). However, the discrepancy in impedance matching restricts their ability to absorb EMW efficiently. This study synthesized a novel composite material, CoFe/C@N, S-rGO, by combining diazo coupling reactions, solvothermal techniques, and high-temperature pyrolysis. The composite consists of cobalt iron/carbon (CoFe/C) nanoparticles embedded in N and S co-doped reduced graphene oxide (N, S-rGO). The co-doping of N and S on graphene oxide (SGO) resulted in numerous defects and disordered sites, which generated interfacial and dipole polarization. The EMW absorption characteristics of the CoFe/C@N, S-rGO can be tuned by varying the quantity of SGO added. Notably, at an SGO concentration of 60 mg, the produced composite exhibits a minimal reflection loss of −53.8 dB, while a thickness of 4.0 mm yields an effective absorption bandwidth of 7.2 GHz. This material’s exceptional EMW absorption capabilities are primarily attributed to interface polarization, multiple reflections, dipole polarization, natural resonance, and eddy current loss. The findings of this study provide a potential solution for enhancing the impedance matching and electromagnetic wave absorption performance of MOFs.

Synthesis of in situ grown CNTs on MOF-derived Ni@CNT with tailorable microstructures toward regulation of electromagnetic wave absorption performance

Metal-Organic framework (MOF) derivatives have been applied as electromagnetic wave absorption (EMA) materials in recent years. Carbon nanotubes (CNTs) can achieve in situ growth on the surface of MOF derivatives. However, there is limited research on the EMA performance by regulating the morphology of the in situ grown CNTs. In this work, we prepared MOF-derived Ni@carbon nanotubes (Ni@CNT) with controllable length of CNTs by solvothermal and simple one-step pyrolysis method and revealed the CNT growth mechanism. We further investigated the effect of in situ grown CNT morphology on electromagnetic parameters and EMA performance. In situ grown CNTs of similar length on the surface of MOF derivatives lead to similar electromagnetic parameters. When the length of CNTs is short, the relaxation strength (Δε=εs−ε∞) is high, leading to excellent microwave absorption performance. For Ni@CNT-600, the reflection loss of −44.4 dB can be achieved at merely 1.72 mm. Finite element (FE) simulation was used to evaluate the EMA mechanism of different samples by calculating electric field and polarization strength. This work has explored the electromagnetic wave absorption performance from the perspective of microstructural tailoring, helpful for understanding the unique role of the in situ grown CNTs on the surface of MOF derivatives and investigating the ultra-thin electromagnetic wave absorption materials.

Stratified nanoflower bimetallic cobalt/iron alloy derived from CoFe-MOFs as efficient peroxymonosulfate activator for antibiotics degradation: Performance, mechanism, and toxicity

Co-based metal-organic framework (Co-MOFs) derivative has gained wide attention in the field of advanced oxidative processes (AOPs). However, the degradation efficiency of single cobalt element remains suboptimal and its activation mechanism still needs to be further explored. In this study, stratified nanoflower bimetallic cobalt/iron alloys (CoFe-NC), derived from cobalt/iron bimetallic-organic frameworks (CoFe-MOFs), was synthesized via self-assembly at room temperature, hydrothermal synthesis and high-temperature carbonization processes and their performance as efficient activators of peroxymonosulfate (PMS) for the degradation of antibiotics was evaluated (removal efficiency of 100 % within 40 min, k=0.0951 min−1). The excellent degradation property benefit by specific nano-flowers structure with high specific surface area (424.67 m2/g), the cycle between Co0→Co2+↔ Co3+ and Fe0→Fe2+↔Fe3+, synergistic effect of Co and Fe bimetals. Furthermore, the CoFe-NC/PMS system exhibits exceptionally high cyclic stability (over 85 % degradation efficiency after four times degradation), a wide range of pH (3−11) and resistance to background ion interference (Cl–, H2PO4–, NO3–, HCO3– and HA), and reduced toxicity of the degradation products. Degradation mechanistic studies demonstrated that the activation of PMS by CoFe-NC generated amounts of reactive oxygen species (ROS) (SO4•−, •OH, •O2− and 1O2). Additionally, high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis identified fifteen intermediate degradation products and three possible degradation pathways were proposed. The results highlight the potential of CoFe-NC as a catalyst for antibiotic removal, providing insights into the optimization of bimetallic-organic framework for environmental applications.

The low-dimensional units modulation of 3D floral Fe/Ni@C towards efficient microwave absorption

Metal-organic frameworks (MOF) derivatives have great potential in microwave absorption (MA) due to their customizable components, topology, and high porosity. However, the correlation between the structural parameters of the low-dimensional units and the MA performance of the 3D MOF derivatives remains unclear. Herein, we prepared a series of floral Fe/Ni@C with different petal sizes and aspect ratios to investigate the effect of low-dimensional structural parameters on the MA properties of 3D MOF derivatives. Specifically, we proposed a competitive coordination strategy. By adjusting the ratio of coordination metals, we successfully obtained floral FeNi-MOF-74 with different petal sizes and aspect ratios. Subsequently, the floral Fe/Ni@C was obtained by thermal-field modulation. It shows that, on the one hand, as the petal size increases, the conductive path is extended and the electron hopping is enhanced, thus facilitating the conductivity loss. And, with the rise of the petal aspect ratio, the tip effect is enhanced, which strengthens the polarization loss. On the other hand, the graphitization degree of the carbon components as well as the size and magnetic properties of the alloy particles can be effectively modulated by optimizing the thermal field modulation temperature. Noteworthily, under the conditions of a coordination metal ratio of 1:1 and an annealing temperature of 700 °C, the obtained MOF derivative exhibited excellent microwave absorption (−65.47 dB at 1.56 mm) and broadband (6.09 GHz at 1.76 mm). This strategy provides new ideas for modulating the microstructure and electromagnetic properties of MOF derivatives.

Comparative studies of cobalt hydroxide and nickel hydroxide designed using novel metal tetrafluoroborate as active materials of battery supercapacitor hybrids

Structure directing agent (SDA) can tailor morphology of active materials with preferable surface properties. Ammonium fluoroborate has been proposed as an effective SDA to synthesize metal organic framework (MOF) derivatives in previous reports, where fluoroborate ions play as morphology regulators by providing steric hindrance. Nickel and cobalt hydroxides are intensively used as active materials in battery supercapacitor hybrids (BSHs), owing to high theoretical capacitances and durability. However, previous studies rarely investigate metal specie effects on energy storage and compare electrochemical performance of nickel and cobalt hydroxides particularly in unique synthesis environments. In this study, nickel tetrafluoroborate (Ni(BF4)2) and cobalt tetrafluoroborate (Co(BF4)2) are respectively used as nickel and cobalt sources to synthesize hydroxides as active materials of BSHs. Tetrafluoroborate ions act as SDAs to design favorable morphologies, while 2-methylimidazole is incorporated to control the pH value for facilitating precipitations. The Ni(OH)2 and Co(OH)2 electrodes respectively show specific capacitances (CF) of 1118.5 and 334.3 F/g at 20 mV/s, owing to the preferable alpha-type hydroxide and larger pore volume/width for Ni(OH)2. A BSH consisted of a Ni(OH)2 positive electrode shows a maximum energy density of 64.0 Wh/kg at 700.0 W/kg, and the CF retention of 116 % and Coulombic efficiency of 94 % after 5000 cycles.

MOF-derived Ni3Fe/Ni/NiFe2O4@C for enhanced hydrogen storage performance of MgH2

Magnesium hydride (MgH2) is an important material for hydrogen (H2) storage and transportation owing to its high capacity and reversibility. However, its intrinsic properties have considerably limited its industrial application. In this study, the NiFe-800 catalyst as metal-organic framework (MOF) derivative was first utilized to promote the intrinsic properties of MgH2. Compared to pure MgH2, which releases 1.24 wt% H2 in 60 min at 275 °C, the MgH2-10 NiFe-800 composite releases 5.85 wt% H2 in the same time. Even at a lower temperature of 250 °C, the MgH2-10 NiFe-800 composite releases 3.57 wt% H2, surpassing the performance of pure MgH2 at 275 °C. Correspondingly, while pure MgH2 absorbs 2.08 wt% H2 in 60 min at 125 °C, the MgH2-10 NiFe-800 composite absorbs 5.35 wt% H2 in just 1 min. Remarkably, the MgH2-10 NiFe-800 composite absorbs 2.27 wt% H2 in 60 min at 50 °C and 4.64 wt% H2 at 75 °C. This indicates that MgH2-10 NiFe-800 exhibits optimum performance with excellent kinetics at low temperatures. Furthermore, the capacity of the MgH2-10 NiFe-800 composite remains largely stable after 10 cycles. Moreover, the Mg2Ni/Mg2NiH4 acts as a “hydrogen pump”, providing effective diffusion channels that enhance the kinetic process of the composite during cycling. Additionally, Fe0 facilitates electron transfer and creates hydrogen diffusion channels and catalytic sites. Finally, carbon (C) effectively prevents particle agglomeration and maintains the cyclic stability of the composites. Consequently, the synergistic effects of Mg2Ni/Mg2NiH4, Fe0, and C considerably improve the kinetic properties and cycling stability of MgH2. This work offers an effective and valuable approach to improving the hydrogen storage efficiency in the commercial application of MgH2.

Growth behavior of anisotropic monometallic MOFs derivatives with the high absorbing and thermal properties

The growth behavior and morphological characteristics of metal-organic frameworks (MOFs) should be considered as important factors in understanding their structure. Therefore, MOFs with atypical shapes, heterogeneous structures or abnormal properties that grow anisotropic can serve as components and templates for further directed assembly or conversion into MOF derivatives with excellent performance in electromagnetic wave absorption. Cobalt (Co) and nickel (Ni) metals have good magnetic properties and are common materials for the preparation of monometallic MOF-derived. In this study, various MOF materials with anisotropic properties, such as rod-like, flower-like, and braided, were prepared by adjusting the molar ratio of Co and Ni solvent to the organic ligand. Due to the rich inter-facial polarization and strong magnetic coupling network of the magnetic composites, Ni-MOF-b (Ni-MOF with braided shape) was prepared for the first time when the molar ratio of nickel nitrate to linker was 1:1.2. The Ni-C-b was obtained after pyrolysis of Ni-MOF-b, the minimum reflection loss of Ni-C-b was –50.7 dB at 4.0 mm. In addition, the thermal conductivity of the film prepared with Ni-C-b as filler is 2.2 W/mK. The film with integrated good heat dissipation and wave absorbing properties provides a research idea for the design of multifunctional integrated film.

Optimizing MOF‐Derived Electromagnetic Wave Absorbers through Gradient Pore Regulation for Pareto Improvement

AbstractPorous materials emerging as potential high‐efficiency electromagnetic (EM) wave absorbers confront a critical trade‐off between impedance matching and attenuation capability. In this study, a versatile strategy is reported to overcome this challenge by constructing gradient pores via solvent‐assisted linker exchange for the fabrication of metal‐organic framework (MOF) derived Fe/Fe3Co7/Co/C composites with high porosity. The impedance and attenuation characteristics of single‐pored and gradient‐pored derivatives are investigated through combined experimental and simulation approaches. Simulated space EM field, loss density, and Smith charts reveal significantly enhanced EM interactions and optimized impedance within the pores. Compared to individual MOF derivatives, the gradient derivative exhibits improved impedance matching from the large‐pored shell and superior attenuation capability from the small‐pored core, giving rise to a Pareto improvement in EM absorption with strong reflection loss (−64.7 dB) and wide effective adsorption bandwidth (5.8 GHz) at a thickness of 2.5 mm. This work not only advances a novel gradient pore strategy for constructing efficient absorbers with enhanced impedance matching and attenuation capability, but also sheds light on the underlying mechanisms of EM interaction with varied porosity, offering insights for extended designs in magnetic, electric and optic devices.

Study on Ce-MOF-derived oxides as morphology-tunable catalyst supports for dry reforming of methane

Dry reforming of methane (DRM) using CH4 and CO2 as feedstocks to catalytically produce high-value synthesis gas products has great application prospects. However, as a high-temperature heterogeneous catalytic reaction, the challenge lies in preparing efficient and stable catalysts for long-term operation. To enhance the catalytic performance by optimizing support, this study proposed regulating the catalyst structure and properties using Ce-based metal-organic framework (MOF) derivatives. Compared with the conventional Ni/CeO2, Ni/CeO2-MOF catalysts performed better in DRM. Especially, Ni/CeO2-UiO-66 demonstrated significant improvement in both catalytic activity and stability. It was also noticed that the Ni/CeO2-MOF catalysts had a potential benefit in limiting the conversion of carbon species to inactive forms given the relatively lower carbon gasification temperatures at their surfaces. The advantage of Ni/CeO2-MOF catalysts was attributed to their better void structure and reduction characteristics, as well as higher oxygen vacancy concentration and improved CO2 adsorption activation capability after pre-activation. This study revealed that MOF-derived supports had distinctive structural characteristics, which were manifested as an important component in high-temperature catalyst systems.

Facile manufacturing of carbon nanotube/ZIF-67-derived cobalt composite aerogel with high-efficiency electromagnetic wave absorption

Developing high-efficiency electromagnetic wave (EMW) absorbers by designing dielectric/magnetic components and microstructure in a straightforward, scalable method is highly desirable yet challenging. Here, we introduce a novel hierarchical composite aerogel-based EMW absorber composed of conductive carbon nanotubes (CNTs) and magnetic metal-organic framework (MOF) derivatives, integrated with sustainable cellulose nanofibers (CNF) derived carbon. This composite was prepared using a scalable freeze-casting followed by carbonization approach. Freeze casting enabled the creation of porous monoliths with high specific surface areas and customizable pore sizes and porosities, crucial for enhancing EMW reflection and scattering. Carbonization enhanced composite conductivity and stabilized the cobalt (Co)/carbon nanoparticles derived from ZIF-67 within the carbon matrix. CNF-derived carbon facilitated the efficient integration of ZIF-derived Co nanoparticles and CNTs, resulting in a robust 3D aerogel structure. The synergistic effects of CNT conductive paths and Co nanoparticles' magnetic losses provided an efficient route to enhance EMW absorption. Moreover, the creation of numerous heterogeneous interfaces augmented polarization losses, significantly enhancing EMW loss capability. Remarkably, the composite achieved outstanding EMW absorption, with a minimum reflection loss of -71.03 dB at a filling ratio of merely 10 wt.% and an effective absorption bandwidth of 4.64 GHz, comparable to leading EMW absorbers reported to date.

Investigating solvent effects on synthesizing novel cobalt hydroxide and fluoride complex from Co(BF4)2 as active materials of the battery supercapacitor hybrid

Metal-organic framework (MOF) derivatives with tunable pore structure and improved conductivity are intensively designed as electroactive materials. Incorporating structure directing agents (SDA) is beneficial for designing MOF derivatives with excellent electrochemical performances. Ammonium fluoroborate has been reported as an effective SDA, coupled with cobalt salt and 2-methylimidazole, to synthesize zeolitic imidazolate framework-67 (ZIF-67) derivatives for charge storage. However, the synthetic environment for growing cobalt-based active materials is relatively complex. In this study, cobalt tetrafluoroborate (Co(BF4)2) is proposed as a novel cobalt precursor, supplementing cobalt ions and acting as the SDA in a single chemical, to synthesize the cobalt-based electroactive material of energy storage electrodes. Interactions between solvent molecules and solutes play significant roles on the morphology, composition, and electrochemical performance of active materials. Deionized water, methanol and ethanol are used as precursor solvents to understand their effects on material and electrochemical properties. The optimal electrode presents a specific capacitance of 608.3 F/g at 20 mV/s, attributed to the highest electrochemical surface area and evident compositions of cobalt fluoride and hydroxide. A battery supercapacitor hybrid achieves the maximum energy density of 45 Wh/kg at 429 W/kg. The CF retention of 100% and Coulombic efficiency of 99% are achieved after 10,000 cycles.

Advancing Anode Performance in Aqueous Zinc-Ion Batteries: A Review of Metal-Organic Framework-Based Strategies.

Aqueous zinc-ion batteries (AZIBs) are garnering substantial research interest in electric vehicles, energy storage systems, and portable electronics, primarily for the reason that the inexpensive cost, high theoretical specific capacity, and environmental sustainability of zinc metal anodes, which are an essential component to their design. Nonetheless, the progress of AZIBs is hindered by significant obstacles, such as the occurrence of anodic side reactions (SR) and the formation of zinc dendrites. Metal-organic framework (MOF)-based materials are being explored as promising alternatives owing to homogeneous porous structure and large specific surface areas. There has been a rare overview and discussion on strategies for protecting anodes using MOF-based materials. This review specifically aims to investigate cutting-edge strategies for the design of highly stable MOF-based anodes in AZIBs. Firstly, the mechanisms of dendrites and SR are summarized. Secondly, the recent advances in MOF-based anodic protection including those of pristine MOFs, MOF composites, and MOF derivatives are reviewed. Furthermore, the strategies involving MOF-based materials for zinc anode stabilization are presented, including the engineering of surface coatings, three-dimensional zinc structures, artificial solid electrolyte interfaces, separators, and electrolytes. Finally, the ongoing challenges and prospective directions for further enhancement of MOF-based anodic protection technologies in AZIBs are highlighted.

Incorporation anthracene and Cu to NH2-Zr-UiO-67 metal-organic framework: Introducing the simultaneous selectivity and efficiency in photocatalytic CO2 reduction to ethanol

Metal-organic frameworks (MOFs) are considered promising candidates for photocatalytic CO2 reduction (PCR) into valuable organic fuels. However, compared to numerous reports regarding CO, CH4, and CHOOH generation, the explored MOFs have shown limited success in producing alcohols, particularly EtOH, through the PCR strategy. Existing MOFs also suffer from insufficient selectivity and efficiency. This study addresses these limitations by implementing a dual modification strategy on NH2-Zr-UiO-67 MOFs. This strategy involves synthesizing four MOF derivatives with different ratios of redox-active metal sites (Cu) to light absorption antenna (anthracene): 1:1, 2:1, 1:2, and 1:3. The as-synthesized MOFs (denoted as Cu/An (X:X)@NZU67 exhibited a remarkable capability for PCR-to-EtOH, without requiring a photosensitizer. The optimal amount of anthracene plays a crucial role in several aspects: improving light absorption, enhancing CO2 adsorption capacity, and promoting charge transfer/separation. Efficient charge transfer is critical for facilitating the multi-step electron transfer pathway required for ethanol synthesis. Notably, Cu/An (1:2)@NZU67 achieved an ethanol productivity of 624.17 µmolh−1g−1 for EtOH, which is, to the best of our knowledge, the highest efficiency reported for MOFs in PCR-to-EtOH conversion so far. Besides significant performance, the MOF showed 100% selectivity for EtOH production. This work represents a significant milestone in the field of PCR-to-EtOH transformation by providing a new perspective for designing MOF photocatalysts that can simultaneously improve both selectivity and efficiency.

In situ construction of metal organic framework derived FeNiCoSe@NiV-LDH polymetallic heterostructures for high energy density hybrid supercapacitor electrode materials

Metal-organic framework (MOF) derivatives as supercapacitor electrodes are limited by their poor conductivity and capacitance properties. Therefore, it is crucial to improve the performance by constructing a rational structure. Here, MIL-88A is converted into a unique hollow heterostructure FeNiCoSe@NiV layered double hydroxide (FeNiCoSe@NiV-LDH, simplified as FNCS@NVL) by a simple ion-exchange combined with co-precipitation technique. The Ni-Co ratio is modulated by an intermediate optimization strategy. Owing to the multi-metal sites and the unique structure, the designed FNCS@NVL shows excellent electrochemical properties as expected. It exhibits excellent specific capacity (1964.4 F·g−1 at 1 A·g−1) and capacitance retention (82.1 % at 10,000 cycles) at three-electrode setup. In addition, the hybrid supercapacitor (HSC) assembled by FNCS@NVL as the positive electrode and activated carbon as the negative electrode also exhibits a high energy density of 71.9 W h·kg−1 at a power density of 800.01 W·kg−1. These results demonstrate that the designed FNCS@NVL complex is an excellent energy storage material and further validate the great potential of polymetallic materials in energy storage. It provides a unique idea for constructing supercapacitors with high energy density and power density.

Using multi-scale interaction mechanisms in yolk-shell structured C/Co composite materials for electromagnetic wave absorption

Advanced chemical engineering for simultaneous modulation of nanomaterial morphology, defects, interfaces, and structure to enhance electromagnetic and microwave absorption (MA) performance. However, accurately distinguishing the MA contributions of different scale factors and tuning the optimal combined effects remains a formidable challenge. This study employs a synergistic approach combining template protection etching and vacuum annealing to construct a controlled system of micrometer-sized cavities and amorphous carbon matrices in metal-organic framework (MOF) derivatives. The results demonstrate that the spatial effects introduced by the hollow structure enhance dielectric loss but significantly weaken impedance matching. By increasing the proportion of amorphous carbon, the balance between electromagnetic loss and impedance matching can be effectively maintained. Importantly, in a suitable graphitization environment, the presence of oxygen vacancies in amorphous carbon can induce significant polarization to compensate for the reduced conductivity loss due to the absence of sp2 carbon. Through the synergistic effects of morphology and composition, the samples exhibit a broader absorption bandwidth (6.28 GHz) and stronger reflection loss (−61.64 dB) compared to the original MOF. In conclusion, this study aims to elucidate the multiscale impacts of macroscopic micro-nano structure and microscopic defect engineering, providing valuable insights for future research in this field.

A Semi-amorphous Ti-BDC-derived Ti/C nanocomposite for efficient electromagnetic wave absorption

Electromagnetic (EM) interference presents a crippling risk to both human health and the dependability of technological devices. Due to their diverse advantages, metal-organic framework (MOF) derivatives have received much attention in developing novel EM wave-absorbing materials. Nevertheless, achieving desirable EM wave absorption capabilities in magnetic carbon-based absorbers through deliberate adjustment of MOFs remains a difficult task. In this study, a novel nanoporous carbon material (TiO2/C) has been successfully synthesized by a semi-amorphous material (Ti-BDC), which has excellent EM wave absorption properties. In detail, the minimum reflection loss (RL) of −49.7 dB and broad effective absorbing bandwidth (EAB) of 4.16 GHz can be reached with an absorbent thickness of 2.2 mm. The improved performance is mostly due to the dipole polarization of the functional groups and the even distribution of the nanoparticles, which form a seamless network. This promotes the dissipation of polarization and dielectric energy at the interface. In addition, the TiO2 nanoparticles on the carbon material improve the impedance matching, further enhancing the material's absorption performance.

ZIF-67-derived monolithic bimetallic sulfides as efficient persulfate activators for the degradation of ofloxacin

In this study, we successfully synthesized ZIF-67 material on three-dimensional (3D) nickel foam (NF) substrate by co-precipitation method, and then fixed CoSx on NF by hydrothermal vulcanization method to form CoSx/NF. The optimized CoSx/NF can effectively activate peroxymonosulfate (PMS) and improve the degradation efficiency of ofloxacin (OFL). The effects of PMS dosage, reaction temperature, initial pH and co-existing ions on the degradation effect of OFL were investigated in detail. CoSx/NF (1 piece 2 × 2 cm) and PMS (1 mM) in an aqueous solution (pH = 7) degraded 85 % of OFL (20.0 mg/L) within 45 min. This favorable degradation performance is mainly attributed to the enhanced electron transfer capability introduced by the bimetallic material. In addition, CoSx/NF still maintained high degradation effect and stable structure after 5 cycles. Quenching experiments further revealed that radicals •OH and 1O2 play a major role in degrading OFL. In addition, the degradation pathway, ecotoxicity evaluation and degradation mechanism of OFL were comprehensively investigated. In summary, the CoSx/NF catalyst proved to be a highly efficient, stable and recyclable heterogeneous composite, and opened up the possibility of using Metal-organic framework (MOF) derivatives in fields such as wastewater treatment.

Optimizing Integrated-Loss Capacities via Asymmetric Electronic Environments for Highly Efficient Electromagnetic Wave Absorption.

Asymmetric electronic environments based on microscopic-scale perspective have injected infinite vitality in understanding the intrinsic mechanism of polarization loss for electromagnetic (EM) wave absorption, but still exists a significant challenge. Herein, Zn single-atoms (SAs), structural defects, and Co nanoclusters are simultaneously implanted into bimetallic metal-organic framework derivatives via the two-step dual coordination-pyrolysis process. Theoretical simulations and experimental results reveal that the electronic coupling interactions between Zn SAs and structural defects delocalize the symmetric electronic environments and generate additional dipole polarization without sacrificing conduction loss owing to the compensation of carbon nanotubes. Moreover, Co nanoclusters with large nanocurvatures induce a strong interfacial electric field, activate the superiority of heterointerfaces and promote interfacial polarization. Benefiting from the aforementioned merits, the resultant derivatives deliver an optimal reflection loss of -58.9dB and the effective absorption bandwidth is 5.2GHz. These findings provide an innovative insight into clarifying the microscopic loss mechanism from the asymmetric electron environments viewpoint and inspire the generalized electronic modulation engineering in optimizing EM wave absorption.

Green-prepared high-performance electromagnetic wave absorption Ni6W6C/Co2O3@C composites and related broadband absorption device

In recent years, the synthesis of absorbing materials using green and environmentally friendly natural raw materials have become a research topic, but green and environmentally friendly materials with both high performance and simple synthesis steps still need to be developed. In this work, glucose and metal organic framework (MOF) were used to prepare composite materials with strong absorbing ability and low cost. We chose glucose, which is convenient to purchase on the market, as the raw material and constructed MOF derivatives with carbon shell skeleton nanostructures through a simple method of hydrothermal and annealing. Compared to the raw materials of traditional absorbing materials, glucose has environmentally friendly, low-cost and green characteristics. We characterized the microstructure and morphology of the material. In addition, we also analyzed the material composition and absorption mechanism of Ni6W6C/Co2O3@C. We have found from the theoretical analysis and simulation results of transmission lines that the minimum reflection loss (RLmin) value of Ni6W6C/Co2O3@C material at 5.43 GHz and 4.76 mm is −56.68 dB. And the effective absorption bandwidth (EAB) at 2.04 mm can reach 7.12 GHz. We load the best sample to the honeycomb structure, a broadband microwave absorber was designed for simulation. The results show that the broadband microwave absorber can achieve an average electromagnetic wave (EMW) loss of more than 99 % in the 0.3–16.04 GHz frequency band (RL value is less than −20 dB), and an average EMW loss of more than 90 % in the 16.04–18 GHz frequency band (RL value less than −10 dB). The composite structure of glucose and MOF derivatives enhances the dielectric loss of the material and enriches various EMW loss mechanisms. Finally, a green, environmental-friendly, high-performance absorbing material with a simple synthesis method is prepared. These results provide insights into the research on EMW absorption of composite materials and new methods for referring.

Efficient degradation of levofloxacin using peroxymonosulfate activated by a novel magnetic catalyst derived from waste walnut shell biomass

Developing an economical and efficient catalyst derived from biochar and metal-organic frameworks (MOFs) for the activation of peroxymonosulfate (PMS) to degrade pollutants holds promise for practical applications. Herein, a simple in-situ synthesis method was designed to generate zeolitic imidazole framework with Co-based (ZIF-67) on the surface of waste walnut shell biomass, and novel derived magnetic catalysts (BC@CobC, Biochar@Co base Carbon) were obtained by high-temperature carbonization. This structure could avoid the drawbacks of structural collapse and particle agglomeration of MOF derivatives, while the presence of biochar could accelerate electron transfer and improve the activation performance. For the degradation of levofloxacin, the removal rate in the 0.5-BC@CobC/PMS system reached 89.88 % in 15 min with a mineralization of 60.43 % when the dosage of catalyst was 0.01 g L−1. Capture experiments and EPR tests showed that SO4−•, •OH, •O2− and 1O2 were jointly participated in the levofloxacin degradation process. Meanwhile, the BC@CobC/PMS system was minimally affected by the pH, co-existing inorganic anions, and natural active substances. It is worth noting that the BC@CobC/PMS system also had excellent removal effect on other typical organic pollutants, and the removal rate could reach 100 %. Cycling experiments showed that BC@CobC maintained high catalytic activity after multiple recycling. The degradation pathway of levofloxacin was also analyzed. Compared to the existing reports, the catalyst is economically superior, with much improved pollutant removal, and boasts a lower catalyst usage. This work will provide a viable idea in terms of reusing biomass waste and activating PMS for wastewater treatment.