Single Zinc Atoms Anchored on MOF-Derived N-Doped Carbon Shell Cooperated with Magnetic Core as an Ultrawideband Microwave Absorber

Two-phase magnetic nanospheres with magnetic coupling effect encapsulated in porous carbon to achieve lightweight and efficient microwave absorbers

Component selection is crucial for microwave absorbents. Multi-component absorbers are increasingly useful and can be prepared through the rational design and control of various electrical, magnetic, and other auxiliary components. In this paper, Ni3Fe/NiFe2O4 nanospheres with two-phase magnetism were designed for use as a multi-component absorber. Specifically, a Ni3Fe/ NiFe2O4@SPC composite with 3D networks was successfully fabricated by hydrothermal method, high-temperature carbonization for activation, and electrostatic self-assembly. The contact interface and coupling effect between the two magnetic components can promote the attenuation of electromagnetic waves. Moreover, the introduction of porous carbon successfully inhibits the easy aggregation of the magnetic particles. Impressively, with a filling load of 10 wt%, the optimal RL of the prepared Ni3Fe/NiFe2O4@SPC composite reaches -60.6 dB, and the effective absorption bandwidth is 5.2 GHz at 2 mm. The combination of two magnetic components and porous carbon in this multiphase microwave-absorbing composite demonstrates a feasible strategy for designing efficient microwave absorbers in the future.

Multilayered Fe3O4@(ZIF-8)3 combined with a computer-vision-enhanced immunosensor for chloramphenicol enrichment and detection

The misuse and overuse of chloramphenicol poses severe threats to food safety and human health. In this work, we developed a magnetic solid-phase extraction (MSPE) pretreatment material coated with a multilayered metal-organic framework (MOF), Fe3O4 @ (ZIF-8)3, for the separation and enrichment of chloramphenicol from fish. Furthermore, we designed an artificial-intelligence-enhanced single microsphere immunosensor. The inherent ultra-high porosity of the MOF and the multilayer assembly strategy allowed for efficient chloramphenicol enrichment (4.51 mg/g within 20 min). Notably, Fe3O4 @ (ZIF-8)3 exhibits a 39.20% increase in adsorption capacity compared to Fe3O4 @ZIF-8. Leveraging the remarkable decoding abilities of artificial intelligence, we achieved the highly sensitive detection of chloramphenicol using a straightforward procedure without the need for specialized equipment, obtaining a notably low detection limit of 46.42 pM. Furthermore, the assay was successfully employed to detect chloramphenicol in fish samples with high accuracy. The developed immunosensor offers a robust point-of-care testing tool for safeguarding food safety and public health.

Hierarchical Co2 P/CoS2 @C@MoS2 Composites with Hollow Cavity and Multiple Phases Toward Wideband Electromagnetic Wave Absorption

The synergistic effect of hollow cavities and multiple hetero-interfaces displays huge advantages in achieving lightweight and high-efficient electromagnetic wave absorption, but still confronts huge challenges. Herein, hierarchical Co2 P/CoS2 @C@MoS2 composites via the self-sacrificed strategy and a subsequent hydrothermal method have been successfully synthesized. Specifically, ZIF-67 cores first act as the structural template to form core-shell ZIF-67@poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (ZIF-67@PZS) composites, which are converted into hollow Co2 P@C shells with micro-mesoporous characteristics because of the gradient structural stabilities and preferred coordination ability. The deposition of hierarchical MoS2 results in phase transition (Co2 P→Co2 P/CoS2 ), yielding the formation of hierarchical Co2 P/CoS2 @C@MoS2 composites with hollow cavities and multiple hetero-interfaces. Benefiting from the cooperative advantages of hollow structure, extra N,P,S-doped sources, lattice defects/vacancies, diverse incoherent interfaces, and hierarchical configurations, the composites deliver superior electromagnetic wave capability (-56.6 dB) and wideband absorption bandwidth (8.96 GHz) with 20 wt.% filler loading. This study provides a reliable and facile strategy for the precise construction of superior electromagnetic wave absorbents with efficient absorption attenuation.

Advancements in Microwave Absorption Motivated by Interdisciplinary Research

Microwave absorption materials (MAMs) are originally developed for military purposes, but have since evolved into versatile materials with promising applications in modern technologies, including household use. Despite significant progress in bench-side research over the past decade, MAMs remain limited in their scope and have yet to be widely adopted. This review explores the history of MAMs from first-generation coatings to second-generation functional absorbers, identifies bottlenecks hindering their maturation. It also presents potential solutions such as exploring broader spatial scales, advanced characterization, introducing liquid media, utilizing novel toolbox (machine learning, ML), and proximity of lab to end-user. Additionally, it meticulously presents compelling applications of MAMs in medicine, mechanics, energy, optics, and sensing, which go beyond absorption efficiency, along with their current development status and prospects. This interdisciplinary research direction differs from previous research which primarily focused on meeting traditional requirements (i.e., thin, lightweight, wide, and strong), and can be defined as the next generation of smart absorbers. Ultimately, the effective utilization of ubiquitous electromagnetic (EM) waves, aided by third-generation MAMs, should be better aligned with future expectations.

Large Microsphere Structure of a Co/C Composite Derived from Co-MOF with Excellent Wideband Electromagnetic Microwave Absorption Performance

In the field of electromagnetic wave (EMW) absorption, carbon matrix materials based on metal-organic frameworks (MOFs) have drawn more interest as a result of their outstanding advantages, such as porous structure, lightweight, controlled morphology, etc. However, how to broaden the effective absorption bandwidth [EAB; reflection loss (RL) ≤ -10 dB] is still a challenge. In this paper, large microsphere structures of a Co/C composite composed of small particle clusters were successfully prepared by the solvothermal method and annealing treatment. At a filling ratio of 40 wt %, the Co/C composite shows attractive microwave absorption (MA) performance after being annealed at 600 °C in an atmosphere of argon. With an EAB of 6.32 GHz (9.92-16.24 GHz) and a thickness of just 2.57 mm, the minimum RL can be attained at -54.55 dB. Most importantly, the EAB can attain 7.12 GHz (10.88-18.0 GHz) when the thickness is 2.38 mm, which is larger than that of the majority of MOF-derived composites. The superior MA performance is strongly related to excellent impedance matching and a higher attenuation constant. This study provides a simple strategy for synthesizing a MOF-derived Co/C composite with a wide EAB.

MOF-derived Co-C composites with 3D star structure for enhanced microwave absorption

The demand of microwave absorption materials (MAMs) with unique morphologies and electromagnetic (EM) balance has become necessary in recent years. Due to the ease of synthesis and tunable structure, metal-organic frameworks (MOFs) are widely used for this special MAMs. In this study, a new three-dimensional hybrid MOF is proposed that is co-doped with six equally branched star morphologies. The Co-C composite has the same six-branched morphology as that of the precursor. When the EM wave is incident, this special structure makes it easier for the EM wave to enter the material vertically due to the expansion of the incident surface, which is effective in adjusting the transmission path of the electron and the reflection and distribution of the EM wave. Because of the special morphology and magneto-dielectric synergy, the Co-C composite shows a minimum reflection loss (RLmin) of -48.5 dB at 11.0 GHz at an absorption thickness of 3.0 mm, with a microwave absorption bandwidth (EAB) of 6.1 GHz. This research provides a practical guidance for preparing the MAMs of special star structure.

Zn Single Atoms/Clusters/Nanoparticles Embedded in the Hybrid Carbon Aerogels for High-Performance ORR Electrocatalysis

Carbon-supported zinc single-atom catalysts have received considerable attention in the electrocatalytic oxygen reduction reaction (ORR) owing to the strong reduction capacity of zinc atoms and the abundant reserves of zinc elements. The common preparation method has been limited to the high-temperature pyrolysis of nitrogen-rich organic molecules and zinc ions, which makes it difficult to further improve the ORR performance. Herein, we first prepared ZnO/PNT/rGO aerogels as precursors via a simple hydrothermal method combined with freeze-drying, in which reduced graphene oxides (rGO) and polypyrrole nanotubes (PNT) together assembled into three-dimensional frames and numerous ZnO nanoparticles were anchored in the three-dimensional skeletons. Then, ZnO/PNT/rGO aerogels were calcined at 800 °C in the argon atmosphere, in which PNT/rGO were derived carbon aerogels, ZnO nanoparticles were reduced to Zn0 by carbon, and generating zinc single atoms were captured by the surrounding nitrogen atoms or aggregated into Zn clusters/nanoparticles in the carbon substrates. The obtained products were Zn single atoms/clusters/nanoparticles embedded into PNT/rGO-derived carbon aerogels, named Zn/NC catalysts. Zn/NC catalysts display a much higher half-wave potential and a larger limiting current density than pure rGO aerogels, NC, and Zn/C catalysts, indicating the synergy of excellent electronic transportation, high mass efficiency from outstanding porosity, and several active centers. Tailoring the quantity of zinc acetate can provide the optimal ORR performance with the Eonset of 0.96 V, the E1/2 of 0.845 V, and remarkable durability. This work exploits a novel strategy of carbon thermal reduction to construct high-performance Zn-based low-dimensional ORR catalysts.

Hierarchical Carbon Network Composites Derived from ZIF-8 for High-Efficiency Microwave Absorption

Metal-organic framework (MOF)-derived composites have gained wide attention due to their specific structures and enhanced performance. In this work, we prepared carbon nanotubes with Fe nanoparticles connected to two-dimensional (2D) hierarchical carbon network composites via a low-pressure gas-solid reaction strategy. Specifically, the three-dimensional (3D) networks derived from ZIF-8 exploited the carbon nanotubes with the function of charge modulation. Meanwhile, we utilized the interconnected 2D nanostructures to optimize impedance matching and facilitate multiple scattering, ultimately improving the overall microwave absorption performance. Furthermore, based on the well-designed structures, the composites prepared at 800 °C (Fe-N-C@CNTs-800) achieved the best reflection loss (RL) of -58.5 dB, thereby obtaining superior microwave absorption performance. Overall, this study provides a good groundwork for further investigation into the modification and dimension design of novel hierarchical microwave absorbers.

Controllable Architecture of ZnO/FeNi Composites Derived from Trimetallic ZnFeNi Layered Double Hydroxides for High-Performance Electromagnetic Wave Absorbers

The optimization design of micro-structure and composition is an important strategy to obtain high-performance metal-based electromagnetic (EM) wave absorption materials. In this work, ZnO/FeNi composites derived from ZnFeNi layered double hydroxides are prepared by a one-step hydrothermal method and subsequent pyrolysis process, and can be employed as an effective alternative for high-performance EM wave absorber. A series of ZnO/FeNi composites with different structures are obtained by varying the molar ratios of Zn²⁺ /Fe³⁺ /Ni²⁺ , and the ZnO/FeNi composites with a Zn²⁺ /Fe³⁺ /Ni²⁺ molar ratio of 6:1:3 show a hierarchical flower-like structure. Owing to the strong synergistic loss mechanism of dielectric-magnetic components and favorable structural features, this hierarchical flower-like ZnO/FeNi sample supplies the optimal EM wave absorption performance with the highest reflection loss of -52.08 dB and the widest effective absorption bandwidth of 6.56 GHz. The EM simulation further demonstrates that impedance matching plays a determining role in EM wave absorption performance. This work provides a new way for the fabrication of a high-performance metal-based EM wave absorber.

An Ion-Engineering Strategy to Design Hollow FeCo/CoFe2 O4 Microspheres for High-Performance Microwave Absorption

Although assembled hollow architectures have received considerable attention as lightweight functional materials, their uncontrollable self-aggregation and tedious synthetic methods hinder precise construction and modulation. Therefore, this study proposes a bi-ion synergistic regulation strategy to design assembled hollow-shaped cobalt spinel oxide microspheres. Dominated by the coordination-etching effects of F^- and the hydrolysis-complex contributions of NH₄ ⁺ , the unique construction is formed attributed to the dynamic cycles between metal complexes and precipitates. Meanwhile, their basic structures are perfectly retained after reduction treatment, enabling FeCo/CoFe₂ O₄ bimagnetic system to be obtained. Subsequently, in-depth analyses are conducted. Investigations reveal that multiscale magnetic coupling networks and enriched air-material heterointerfaces contribute to the remarkable magnetic-dielectric behavior, supported by the advanced off-axis electron holography technique. Consequently, the obtained FeCo/CoFe₂ O₄ composites exhibit excellent microwave absorption performances with minimal reflection losses (RL_min ) as high as -51.6 dB, an effective absorption bandwidth (EAB) of 4.7 GHz, and a matched thickness of 1.4 mm. Thus, this work provides an informative guide for rationally assembling building blocks into hollow architectures as advanced microwave absorbers through bi-ion and even multi-ion synergistic engineering mechanisms.

Controllable preparation of 2D carbon paper modified with flower-like WS2 for efficient microwave absorption

In the practical application of microwave absorbing materials, traditional powder materials need to be mixed with the matrix to fabricate composite coatings. However, the complex preparation process of composite coatings and the uneven dispersion of powders in the matrix limit their application. To solve these problems, two-dimensional (2D) F-WS₂/CP composite films were prepared by using carbon paper (CP) as a dispersion matrix and loading flower-like WS₂ on its surface through a simple hydrothermal method. The morphology and microwave absorption (MA) performance of the composite films are easily regulated by adjusting the amount of reaction precursors. The combination of WS₂ and CP facilitates impedance matching and improves the electromagnetic wave attenuation performance based on the synergistic effect of different loss mechanisms including multiple reflections and scattering, interfacial polarization, dipolar polarization, and conduction loss. At a low filler content (5 wt%), the maximum reflection loss (RL) of the composite film is up to -50 dB (99.999% energy absorption) at 12.5 GHz with 2.8 mm thickness. Moreover, at a relatively thin 1.8 mm thickness, its maximum RL remains -35 dB (>99.9% energy absorption). The as-prepared composite film shows excellent MA properties at a thinner thickness and lower filling content, providing inspiration for the preparation of light weight and efficient 2D thin-film microwave absorbers in the future.

Engineering of the Core-Shell Boron Nitride@Nitrogen-Doped Carbon Heterogeneous Interface for Efficient Heat Dissipation and Electromagnetic Wave Absorption

The effective integration of multiple functions into electromagnetic wave-absorbing (EWA) materials is the future development direction but remains a huge challenge. A rational selection of components and the design of structures can make the material have excellent EWA performance and heat dissipation. Herein, the core-shell structured boron nitride@nitrogen-doped carbon (BN@NC) is prepared by using waterborne polyurethane (WPU) as the carbon source via a facile pyrolysis treatment process, where NC is used as the conductive loss shell, and BN serves as an impedance matching core and dominant heat transfer media. As a result, the BN@NC-900 filled with paraffin wax yields a minimum reflection loss of -42.2 dB at 2.2 mm and an effective absorbing bandwidth of 4.48 GHz at 1.8 mm, and its thermal conductivity reaches up to 0.92 W/m·K in epoxy resin. Most importantly, flexible BN@NC/WPU films are prepared and simultaneously achieve the dual-functional capability of efficiently dissipating heat and electromagnetic waves (-50.0 dB). Besides, an attractive multiband absorption feature (>99%) from C to Ku bands is realized and a strong absorbing over -27.0 dB at the S band (2.88 GHz) is even achieved. This study may pave a new route for the rational design of multifunctional EWA materials.

Phase Transition Induced via the Template Enabling Cocoon-like MoS2 an Exceptionally Electromagnetic Absorber

Structural engineering via the template method is efficient for micro-nano assembling. However, only structural design and lack of composition control restrict their advanced application. To overcome this issue, applying a template to simultaneously realize the structural design and fine component control is highly desired, which has been ignored. In this study, a spinel-shaped MoS₂ heterostructure with controlled phase ratios of 1H and 2H phase is developed using the AlOOH template method. This work demonstrates that the MoS₂ phase transition mechanism from 2H to 1T is substantially attributed to the close exposed crystal's surface and approximately accordant surface energy. The superiority and additional proof are provided based on density-functional theory simulation, transmission electron microscope holography, etc. With an effective absorptance region of 6.3 GHz under a thickness of 1.4 mm, the reported samples present outstanding microwave absorption capacity. This is attributed to the beneficial coupled effect between the well-designed structure and phase regulation. This work offers valuable insights into structural engineering and component regulation template methods.

Synergistically Constructed Electromagnetic Network of Magnetic Particle-Decorated Carbon Nanotubes and MXene for Efficient Electromagnetic Shielding

Lightweight polymer-based nanostructured aerogels are crucial for electromagnetic interference (EMI) shielding to protect electronic devices and humans from electromagnetic radiation. The construction of three-dimensional (3D) conductive networks is crucial to realize the excellent electromagnetic shielding performance of polymer-based aerogels. However, it is difficult to realize the interconnection of different conductive fillers in the polymer matrix, which limits the further improvement of their performance. Herein, 3D ordered hierarchical porous Fe₃O₄-decorated carbon nanotube (Fe₃O₄@CNT)/MXene/cross-linked aramid nanofiber (c-ANF)/polyimide (PI) aerogels were prepared via a unidirectional freezing strategy. Benefiting from the magnetic loss effect of Fe₃O₄ magnetic nanoparticles, the conductive and dielectric loss effects of CNTs, and the multiple reflections induced by the 3D ordered hierarchical porous structure, the Fe₃O₄@CNTs/MXene/c-ANFs/PI (FMCP) aerogels with the same contents of 8 wt % of Fe₃O₄@CNTs and MXene exhibit a high absolute EMI shielding effectiveness (SE) of up to 67.42 dB and a microwave reflection (SE_R) of 0.60 dB. More importantly, the phase transition of a small amount of MXene to TiO₂ optimizes the impedance matching and transmission and then improves the microwave absorption. The FMCP aerogel has an outstanding normalized surface specific SE (SSE/t) which is up to 62,654 dB cm²·g^-1. Meantime, the FMCP aerogels also show super-elasticity and could maintain 91.72% of the maximum stress after 1000 cycles of compression release under a fixed deformation of 60%.

Texture Regulation of Metal-Organic Frameworks, Microwave Absorption Mechanism-Oriented Structural Optimization and Design Perspectives

Texture regulation of metal-organic frameworks (MOFs) is essential for controlling their electromagnetic wave (EMW) absorption properties. This review systematically summarizes the recent advancements in texture regulation strategies for MOFs, including etching and exchange of central ions, etching and exchange of ligands, chemically induced self-assembly, and MOF-on-MOF heterostructure design. Additionally, the EMW absorption mechanisms in approaches based on structure-function dependencies, including nano-micro topological engineering, defect engineering, interface engineering, and hybrid engineering, are comprehensively explored. Finally, current challenges and future research orientation are proposed. This review aims to provide new perspectives for designing MOF-derived EMW-absorption materials to achieve essential breakthroughs in mechanistic investigations in this promising field.

Ion-Exchange Strategy for Metal-Organic Frameworks-Derived Composites with Tunable Hollow Porous and Microwave Absorption

Hollow metal-organic frameworks (MOFs) with careful phase engineering have been considered to be suitable candidates for high-performance microwave absorbents. However, there has been a lack of direct methods tailored to MOFs in this area. Here, a facile and safe Ni²⁺ -exchange strategy is proposed to synthesize graphite/CoNi alloy hollow porous composites from Ni²⁺ concentration-dependent etching of Zeolite imidazole frame-67 (ZIF-67) MOF and subsequent thermal field regulation. Such a special combination of hollow structure and carefully selected hybrid phase are with optimized impedance matching and electromagnetic attenuation. Especially, the suitable carrier transport model and the rich polarization site enhance the dielectric loss, while more significant hysteresis loss and more natural resonance increase the magnetic loss. As a result, excellent microwave absorbing (MA) performances of both broadband absorption (7.63 GHz) and high-efficiency loss (-63.79 dB) are obtained. Moreover, the applicability and practicability of the strategy are demonstrated. This work illustrates the unique advantages of ion-exchange strategy in structure design, component optimization, and electromagnetic regulation, providing a new reference for the 5G cause and MA field.

Magnetic Interacted Interaction Effect in MXene Skeleton: Enhanced Thermal-Generation for Electromagnetic Interference Shielding

With the rapid advancements of portable and wearable equipment, high-efficiency electromagnetic interference (EMI) shielding materials are highly entailed to eliminate radiated electromagnetic pollution. Herein, by assembling hexagonal SrFe₁₂ O₁₉ flakes into a Ti₃ C₂ T_x MXene/MWCNT substrate, a magnetized Ti₃ C₂ T_x -based film is successfully fabricated by a facile filtration approach. Carbon nanotubes are used as isolation agents to realize the submicroscopic dispersion of MXene and SrFe₁₂ O₁₉ . The obtained MXene/MWCNTs/SrFe₁₂ O₁₉ film shows a high electrical conductivity of 438 S cm^-1 and an excellent EMI shielding effectiveness of 62.9 dB in X-band at a thickness of only 40 µm. Benefiting from a strong magnetic response ability and an expanded magnetic coupling space, hexagonal SrFe₁₂ O₁₉ sheets can efficiently consume incident magnetic field energy by domain wall migration and the ferromagnetic resonance effect. Boosted EMI shielding performance can be achieved by improving the magnetic loss in the Ti₃ C₂ T_x MXene/MWCNTs/SrFe₁₂ O₁₉ film, preventing the secondary reflection of electromagnetic waves. Meanwhile, magnetized MXene-based films display the freestanding and flexible features and are suitable for installation in electric devices. It is anticipated that this strategy offers new ideas for designing EMI shielding films and in broadening potential utility of MXene-based materials.

Dimensional Design and Core-Shell Engineering of Nanomaterials for Electromagnetic Wave Absorption

Electromagnetic (EM) wave absorption materials possess exceptionally high EM energy loss efficiency. With vigorous developments in nanotechnology, such materials have exhibited numerous advanced EM functions, including radiation prevention and antiradar stealth. To achieve improved EM performance and multifunctionality, the elaborate control of microstructures has become an attractive research direction. By designing them as core-shell structures with different dimensions, the combined effects, such as interfacial polarization, conduction networks, magnetic coupling, and magnetic-dielectric synergy, can significantly enhance the EM wave absorption performance. Herein, the advances in low-dimensional core-shell EM wave absorption materials are outlined and a selection of the most remarkable examples is discussed. The derived key information regarding dimensional design, structural engineering, performance, and structure-function relationship are comprehensively summarized. Moreover, the investigation of the cutting-edge mechanisms is given particular attention. Additional applications, such as oxidation resistance and self-cleaning functions, are also introduced. Finally, insight into what may be expected from this rapidly expanding field and future challenges are presented.

State of the Art and Prospects in Metal-Organic Framework-Derived Microwave Absorption Materials

Microwave has been widely used in many fields, including communication, medical treatment and military industry; however, the corresponding generated radiations have been novel hazardous sources of pollution threating human's daily life. Therefore, designing high-performance microwave absorption materials (MAMs) has become an indispensable requirement. Recently, metal-organic frameworks (MOFs) have been considered as one of the most ideal precursor candidates of MAMs because of their tunable structure, high porosity and large specific surface area. Usually, MOF-derived MAMs exhibit excellent electrical conductivity, good magnetism and sufficient defects and interfaces, providing obvious merits in both impedance matching and microwave loss. In this review, the recent research progresses on MOF-derived MAMs were profoundly reviewed, including the categories of MOFs and MOF composites precursors, design principles, preparation methods and the relationship between mechanisms of microwave absorption and microstructures of MAMs. Finally, the current challenges and prospects for future opportunities of MOF-derived MAMs are also discussed.

High-Density Anisotropy Magnetism Enhanced Microwave Absorption Performance in Ti3C2Tx MXene@Ni Microspheres

Two-dimensional materials, especially the newly emerging MXene, have attracted numerous interests in the fields of energy conversion/storage and electromagnetic shielding/absorption. However, the inherently inevitable aggregation and absence of magnetic loss of MXene considerably limit its electromagnetic absorption application. The introduction of magnetic component and favorable structural engineering are the alternatives to improve the microwave absorption (MA) performance. Herein, we report a spheroidization strategy to assemble double-shell MXene@Ni microspheres, where the commonly lamellar MXene are reshaped into three-dimensional microspheres that provide the substrate for oriented growth of Ni nanospikes. Whereas this structural feature offers massive accessible active surfaces that effectively promote the dielectric loss ability, the introduction of magnetic Ni nanospikes enables the additional magnetic loss capacity. Benefiting from these merits, the synthesized 3D MXene@Ni microspheres exhibit superior MA performance with the minimum reflection loss value of -59.6 dB at an ultrathin thickness (∼1.5 mm) and effective absorption bandwidth of 4.48 GHz. Moreover, the electron holography results reveal that the high-density anisotropy magnetism plays an important role in the improvement of MA performance, which provides an insight for the design of MXene-based materials as high-efficient microwave absorbers.

Synergetic Dielectric and Magnetic Losses of a Core-Shell Co/MnO/C Nanocomplex toward Highly Efficient Microwave Absorption

High-performance microwave-absorbing materials (MAMs) derived from metal-organic frameworks (MOFs) have attracted considerable attention due to their tunable chemical composition and microstructure. In this contribution, a core-shell-structured Co/MnO/C nanocomplex was prepared using a CoMn-MIL MOF by a facile hydrothermal synthesis and subsequent pyrolysis process. The optimal microwave absorption (MA) property of the as-prepared Co/MnO/C nanocomplex was achieved by the regulation of the Co²⁺/Mn²⁺ molar ratio. The minimum reflection loss (RL_min) of the Co/MnO/C-31 nanocomplex was low to -55.0 dB at 16.2 GHz with a thickness of 1.49 mm, and the effective absorption bandwidth (EAB) was high to 5.95 GHz (12.05-18 GHz) at a thickness of 1.8 mm. The mixed-metal nanocomplex with the core-shell structure exhibited outstanding MA performance, corresponding to the synergetic effect of the magnetic and dielectric loss. It provides a high efficiency strategy for rendering low reflection loss and broad EAB to high-performance MAMs.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities

Electromagnetic (EM) absorbers play an increasingly essential role in the electronic information age, even toward the coming "intelligent era". The remarkable merits of heterointerface engineering and its peculiar EM characteristics inject a fresh and infinite vitality for designing high-efficiency and stimuli-responsive EM absorbers. However, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. Herein, EM response mechanisms of interfacial effects are dissected in depth, and with a focus on advanced characterization as well as theoretical techniques. Then, the representative optimization strategies are systematically discussed with emphasis on component selection and structural design. More importantly, the most cutting-edge smart EM functional devices based on heterointerface engineering are reported. Finally, current challenges and concrete suggestions are proposed, and future perspectives on this promising field are also predicted.

Dumbbell-Like Fe3O4@N-Doped Carbon@2H/1T-MoS2 with Tailored Magnetic and Dielectric Loss for Efficient Microwave Absorbing

Ferroferric oxide (Fe₃O₄)/C composites have received much attention as a result of converting electromagnetic waves to heat for harvesting efficient electromagnetic wave (EMW) absorbing performance. However, the practical EMW absorbing of these absorbers is still greatly hindered by the unmatched impedance properties and limited EMW absorbing ability. Tuning the morphologies at nanoscale and assembling the nanoarchitecture construction are essential to address this issue. Herein, dumbbell-like Fe₃O₄@N-doped carbon (NC)@2H/1T-MoS₂ yolk-shell nanostructures are rationally designed and fabricated via a facile etching and wet chemical synthesis strategy. By manipulating the etching time toward the magnetic Fe₃O₄ component, the dielectric and magnetic loss of absorbers could be well-tuned, thus achieving the optimized impedance characteristics. As a result, the maximum refection losses (RL_maxs) of Fe₃O₄@NC-9h and Fe₃O₄@NC-15h are -19.8 dB@7.9 GHz and -39.5 dB@8.3 GHz, respectively. Moreover, the MoS₂ nanosheets with a mixed 2H/1T phase anchored on Fe₃O₄@NC-15h (Fe₃O₄@NC-15h@MoS₂) further boost the RL_max to -68.9 dB@5.8 GHz with an effective absorbing bandwidth of ∼5.25 GHz. The tailored synergistic effect between dielectric and magnetic loss and the introduced interfacial polarization (Fe₃O₄@NC/MoS₂) are discussed to explain the drastically enhanced microwave absorbing ability. This work opens up new possibilities for effective manipulation of electromagnetic wave attenuation performance in magnetic-dielectric-type nanostructures.

Liquid metal coated copper micro-particles to construct core-shell structure and multiple heterojunctions for high-efficiency microwave absorption

Facing the inherent defects of magnetic materials, the research of non-magnetic absorbers has gradually become a new direction in the research of microwave absorbers to fit the requirements of a new generation for high strength, wide effective absorption bandwidth. Herein, the liquid metal and copper (LC) composite micro-particles with multiple heterojunctions and core-shell structure, which have an excellent performance of microwave absorption (MA), were prepared by simply coating liquid metal on copper and then annealing. These special LC composite micro-particles exhibit excellent MA performance with the optimal reflection loss of -39.6 dB at thickness of 2.1 mm and a maximum effective absorption bandwidth of 4.96 GHz at thickness of 2.5 mm. The high MA performance of the LC composite particles are due to the enhancement of dielectric loss, including dipolar, interfacial, and dielectric polarization, which is caused by the special core-shell structure, multiple interfaces and heterojunctions. Furthermore, the multiple reflection/scattering of microwaves among particles or on the surface of particles also benefit to the high MA performance. Therefore, this study provides a facile method to construct multiple metal heterojunctions which have great prospects in microwave absorption applications.