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Highlights: In terms of components and structures, this review summarizes progresses and highlights strategies of MOF derivatives for efficient electromagnetic wave absorption. We also systematically delineate relevant theories and points out the prospects and current challenges. To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are urgently explored. Metal–organic framework (MOF) derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures, which is expected to satisfy diverse application requirements. The extensive developments on MOF derivatives demonstrate its significantly important role in this research area. Particularly, MOF derivatives deliver huge performance superiorities in light weight, broad bandwidth, and robust loss capacity, which are attributed to the outstanding impedance matching, multiple attenuation mechanisms, and destructive interference effect. Herein, we summarized the relevant theories and evaluation methods, and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field. In spite of lots of challenges to face, MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) carbon-based materials have attracted growing attention in the field of electromagnetic wave absorption applications. However, their high conductivity results in high dielectric constant, leading to impedance mismatching, and this characteristic finally weakens their electromagnetic wave absorption performance. In this work, 3D carbon foam (3DCF) was successfully prepared by calcining the melamine foam as the carbon framework precursor under N 2 atmosphere. Subsequently, 1T-2H MoS 2 nanosheets were uniformly assembled on the surface of the 3DCF skeleton through a solvothermal process. The diameter of the 3DCF skeleton was about 1 μm and the thickness of the 1T-2H MoS 2 on the surface was about 150 nm. The 3D network brings in many advantages for microwave attenuation, including numerous conductive pathways, excellent impedance matching and multi-polarization processes. The composites exhibited a maximum reflection loss (RL max) of −45.88 dB at 10.2 GHz with the thickness of 2.2 mm, and the effective absorbing bandwidth (E AB) was as wide as 5.68 GHz, implying their superb microwave absorption behavior. This work is believed to offer a strategy for the design of efficient 3D electromagnetic wave absorbers with low density in the future. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) carbon foams (CF) embedded with CuNi alloy nanoparticles have been constructed for electromagnetic wave absorption application. In the synthetic procedure, Ni2+ and Cu2+ were firstly adsorbed into the melamine foam (MF) to form Ni2+-Cu2+/MF composites, which were then subject to the pyrolysis treatment, resulting in the production of mesoporous CuNi alloy/CF. The texture characterizations indicate that CuNi alloy nanoparticles whose size distribution was 20–600 nm were embedded on the surface of the CF. Other than previous carbon structures, the CuNi/CF with CuNi alloy nanoparticles evenly distributed into the 3D carbon matrix inherits the characteristic of the 3D structured N-rich MF, which induces masses of dipole polarization, interfacial polarization and electromagnetic wave scattering. The CuNi11 exhibits excellent electromagnetic wave absorption performance with the reflection loss (RL) of −50.20 dB at a thin thickness of 1.6 mm. This work highlights the effect of metal compositions on the electromagnetic wave absorption performance and provides an environmentally friendly, low cost and easy-to-large-scale-preparation approach for the design of metal alloy/CF electromagnetic wave absorbers. Image 1 [ABSTRACT FROM AUTHOR]

Large-scale octahedral FeO nanocrystallines with crystalline size of 100−500 nm were synthesized by a facile solvent-thermal method for electromagnetic wave application. The FeO nanocrystallines showed a higher saturation magnetization ( M) value of 86.8 emu/g and larger coercivity ( H) value of 255 Oe than that of magnetite polycrystallines because of their good crystallization and dispersion. The epoxy resin composites with 40 vol% FeO powders provided good electromagnetic wave absorption performance (RL < −20 dB) in the range of 2.0-4.3 GHz over the absorber thicknesses of 3.5-6.8 mm. A minimum RL value of −47 dB was observed at 3.1 GHz with a thickness of 4.8 mm. [ABSTRACT FROM AUTHOR]

Abstract: We report a template-free hydrogen reduction approach to prepare sponge-like cobalt nanoporous structures employing Co3O4 as precursors, which were obtained by thermal-decomposing of CoCO3 intermediates prepared by a facile solvent-thermal route. A three-step formation mechanism for the Co nanoporous structures was proposed. The epoxy resin composites with 65wt.% rhomb-like and rod-like samples showed efficient electromagnetic wave absorption characteristics (RL<−20dB) in the ranges of 12.8–18GHz and 11.2–18GHz over absorber thicknesses of 1.05–1.5mm and 1.0–1.6mm, respectively. It is believed that the porous metallic magnets would gain wide applications as more efficient electromagnetic wave absorbers. [Copyright &y& Elsevier]

[Display omitted] One-dimensional carbon-based materials have emerged as promising electromagnetic wave absorption agents due to their outstanding conductivity, high stability, low weight, and easy availability. Properly optimizing their electromagnetic parameters is expected to further enhance the electromagnetic wave attenuation capacity. In this work, efficient Cu 9 S 5 /C nanocomposite fibers are prepared by a combined approach of electrospinning and subsequent carbonization-sulfurization processes. The Cu 9 S 5 nanoparticles with size of ca. 100–200 nm were homogeneously embedded in fibrous carbon matrix with diameter of 300 nm. For electromagnetic wave absorption, the optimized composited nanofibers (Cu 9 S 5 /C-3) exhibited an extremely superb reflection loss of −65.4 dB (9.5 GHz, 2.7 mm) at a lower mass fraction (20 wt%). And the effective absorption bandwidth could be up to 4.1 GHz (8.0–12.1 GHz) with a matching thickness of 2.9 mm, covering the whole X-band. Electromagnetic wave attenuation mechanism investigation revealed that the performance enhancement originated from the synergy of various loss pathways, including interfacial polarization, dipole polarization, and conductive loss. The unique hierarchical structure from particle embedding, one-dimensional fiber, to three-dimensional network further amplified the performance advantages of each component. This work is anticipated to provide a feasible strategy to synthesize sulfide/carbon binary composite fibers for efficient electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

[Display omitted] Regulating electromagnetic parameters and thus improving impedance matching characteristics by multi-component design is regarded as a prospective approach to obtain highly efficient electromagnetic wave absorption materials. Whereas, it is still challenging to fabricate microwave absorbers with strong absorption capacity and durability in harsh conditions. Based on the above considerations, three-dimensional porous multi-functional manganese oxide/nickel/carbon microspheres had been designed and prepared through a combined approach of facile solvothermal reactions and subsequent carbonization processes. The textural characteristic examinations demonstrated that, numerous manganese oxide and Ni nanoparticles of 15–20 nm in diameter were well dispersed in the carbon-based microspheres of approximately 0.8–1 μm in size. Microwave absorption property evaluation indicated that the minimum reflection loss reached up to −53.6 dB at 9.5 GHz, and effective absorption bandwidth of 3.7 GHz was achieved at matching thickness of merely 2.0 mm. The electromagnetic wave attenuation mechanisms analysis displayed that excellent impedance matching and various dissipation pathways, including magnetic loss, interfacial and dipole polarization relaxation synergistically contributed to the high microwave absorption performances of the porous composites. Radar cross-sectional simulation and photothermal measurements verified that the materials were supposed to have promising foregrounds in complicated circumstances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiple polarizations and losses are enhanced by the Co-N-C particles. • The RL min of PI/rGO/CNC-1 aerogel reaches −75 dB with the EAB max of 7.28 GHz. • The PI/rGO/CNC aerogel integrates excellent multifunctional features. The fabrication of dielectric/magnetic multicomponent hybrids represents a promising strategy for achieving advanced electromagnetic wave (EMW) absorption performances. However, it also poses a significant challenge due to the difficulty in fully utilizing the properties of each component. Here, in this work, metal–organic frameworks (MOFs) derived Co-N-C species were combined with graphene oxide/polyamide acid and then freeze-dried and annealed to produce PI/rGO/CNC aerogels. These aerogels exhibit outstanding EMW absorption properties owing to their multiple heterogeneous interfaces and synergetic electromagnetic losses while retaining satisfying mechanical properties and lightweight features of PI/rGO aerogels. In particular, PI/rGO/CNC-1 aerogel shows the optimal EMW attenuation performance with a minimal reflection loss (RL min) value of –75 dB, and its maximal effective absorption bandwidth (EAB max) is as broad as 7.28 GHz. Moreover, the lightweight nature, elastic feature, structural stability, thermal insulation and hydrophobicity of the PI/rGO/CNC aerogels ensure that they have vast application prospects as advanced EMW absorption materials in complicated environment. [ABSTRACT FROM AUTHOR]

Broadening absorption bandwidth is of great significance to extend application scenarios for electromagnetic wave (EMW) absorption materials. Since the electromagnetic character changes caused by high shape anisotropy, one-dimensional fibrous materials have been widely concerned. In this work, manganese sulfide (MnS)/carbon nanocomposite fibers are facilely synthesized by a facile combination of electrospinning and high-temperature processing. The fibrous carbon supports with a 350-nm average diameter are embedded with dense MnS nanoparticles on the surface. Under the premise of ensuring a strong EMW absorption intensity (−68.9 dB, 11.1 GHz, 3.6 mm), the MnS/carbon nanocomposite fibers can achieve a wide effective absorption bandwidth of 7.2 GHz (9.5–16.7 GHz, 3.3 mm). In-depth study verifies that MnS can help to achieve superior synergy between conductive and polarized attenuation capacity, enhance the attenuation ability and optimize impedance matching characteristic. Besides, considering the few studies about MnS in this field, this work confirmed the huge potentials of MnS for EMW absorption applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The well-designed structures bring about optimized impedance matching, multiple polarization and loss pathways. • The NTMRG-2 aerogel exhibits a RL min of −71.4 dB and a maximum EAB of 6.48 GHz. • The ultralow thermal conductivity (27 mW m−1K−1) and hydrophobicity endow the aerogel with multifunction characteristic. The demand for high-performance electromagnetic wave absorbing (EMA) materials featured with strong attenuation ability, extended absorption bandwidth and ultralight property is imperative yet remains challenging. Herein, a three-dimensional hierarchically porous reduced graphene oxide (rGO)/Ti 3 C 2 T x MXene aerogel embedded with Ni@TiO 2 core–shell microspheres was prepared via directional freeze-drying followed by a mild annealing process. The divergence in structure and multicomponent dielectric/magnetic features bring about optimized impedance matching characteristic, multiple polarization and loss pathways, collectively contributing to the excellent absorption performance. As a result, the Ni@TiO 2 /MXene/rGO (NTMRG-2) aerogel exhibits optimized EMA capability with a maximal effective absorption bandwidth (EAB max) of 6.48 GHz at a lower loading level of 5 wt% in the supporting matrix, covering the whole Ku band. Additionally, it achieves a minimum reflection loss (RL min) of −71.4 dB with a matching thickness of 2.04 mm. Moreover, the aerogel also exhibits an ultra-light density of 5.58 mg cm−3, superior thermal insulation capacity (close to air) and hydrophobicity, underscoring its potential for multiple applications in various scenarios. [ABSTRACT FROM AUTHOR]

High absorption capacity and broad absorption bandwidth electromagnetic wave (EMW) absorption materials (namely, EMW absorbers) are highly desirable due to the interference with electronics and harms on human beings' health. In search for rational design on nanostructured absorbers, we have synthesized and demonstrated the rod-shape composites with Fe-containing magnetic nanoparticles (Fe 3 O 4 , Fe 3 C and Fe NPs) embedded into nano-porous carbon (NPC) through pyrolysis of Fe-based metal-organic frameworks (MOFs). The morphologies, compositions, and graphitization degree of the Fe-MOFs derived magnetic NPC nanorods can be effectively controlled via adjusting the pyrolysis temperatures. The graphitization level has a significant influence on the permittivity of the composites upon variation of pyrolysis temperatures, thereby a tunable electromagnetic wave (EMW) absorption is observed. Consequently, the resulting magnetic NPC nanorods obtained at pyrolysis temperature of 600 and 700 °C exhibit the most remarkable EMW absorption performance with a strong reflection loss of −52.9 dB and broad effective bandwidth (f e) of 4.64 GHz at 3.07 mm. With a thickness of 3.5 mm, the f e for the magnetic NPC nanorods at 600 °C covers the whole X-band from 7.92 to 12.48 GHz. The noticeable EMW absorption performances have been greatly enhanced compared to those reported Fe 3 O 4 based absorbers, owing to the synergy of multiple components and the porous structures inherited from MOFs. Image 1 [ABSTRACT FROM AUTHOR]

Today, electromagnetic wave (EMW) absorbing materials with strong absorption capacity alone are hardly enough to meet the growing problem of EMW pollution. This work is the first designs and synthesizes LaFeO 3 -decorated nitrogen (N)-doped reduced graphene oxide aerogel (LFO/N-rGO) novel composites by a simple hydrothermal method. When the mass ratio of the LaFeO 3 (LFO) nanoparticles: graphene oxide (GO): urea is 1:5:7.5, LFO/N-rGO achieves broadband absorption while possessing strong electromagnetic wave absorption capability. A strong reflection loss (RL) of −64.5 dB is obtained at 9.2 GHz. In addition, the maximum effective absorption bandwidth with a 2.83 mm thickness can reach up to 6.72 GHz. The EMW absorption mechanism analysis shows that the excellent microwave absorption capability is mainly attributed to the enhanced multiple reflections and multi-scattering, enhanced interfacial polarization process, proper conduction loss, and optimized impedance matching characteristics. Herein, this work proposes a new approach to improve the microwave absorption capability of N-doped reduced graphene oxide-based composites and provides a novel strategy to design EMW absorbing materials with wide effective absorption bandwidth and strong absorption capacity. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • MoO 2 modified Ni/CNFs is synthesized by facile electrospinning and carbonization. • Synergistic magnetic-dielectric attenuation conduces to effective EMW absorption. • Polarization behavior is revealed by simulating the electric field distribution. • Far-field EMW absorption competence is forecasted by radar cross section. One-dimensional carbon-based nanofibers are considered as a group of the most promising candidates applied in electromagnetic wave absorption owing to their shape anisotropy, tractability, and stability. To further meet the requirements of lightweight, broadband and effective features, in this work, nickel/carbon nanofibers modified with molybdenum dioxide were resoundingly fabricated through electrospinning and subsequent carbonization. According to textural characteristic analyses, nickel nanoparticles with a diameter of approximately 30 nm were supported on the surface of the carbon nanofibers, while the smaller MoO 2 grains were embedded inside. Under the premise of realizing an outstanding electromagnetic wave absorption intensity (−64.0 dB at 8.0 GHz), the ternary composites achieved a wide effective absorption bandwidth up to 6.9 GHz (9.5 GHz–16.4 GHz). Based on the investigations of electromagnetic parameters and field distribution simulation results, the interwoven network structure and the synergistic effect between each component not only endowed the materials with perfect impedance matching, but introduced manifold loss mechanisms including magnetic loss, conductivity loss and multiple polarization relaxation. Thus, this work provided theoretical guidance and enlightenment for the design of new generation fibrous electromagnetic wave absorbers. [ABSTRACT FROM AUTHOR]

• The MnO@N-doped carbon nanotubes with adjustable carbon content were synthesized. • The synergistic dielectric loss mechanisms were systematically analyzed. • The nanotubes exhibit excellent electromagnetic wave absorption performance. • The polarization behavior is thoroughly analyzed by simulating the electric field. Dielectric loss materials exhibit appealing ability for electromagnetic wave attenuation due to their tunable permittivity, favorable stability and light weight. Herein, MnO@N-doped carbon nanotubes with adjustable carbon layer are synthesized by thermal decomposition of pyrrole on the surface of MnO 2 nanotubes for electromagnetic absorption application. The morphology, composition, internal defects, conductivity and electromagnetic parameters of the composites are fully investigated. By using ANSYS software to simulate the electric field distribution in the material under the excitation of alternating electromagnetic field, the polarization behavior is analyzed in depth. The combination of MnO and carbon endows the composites with enhanced dielectric loss capacity and better impedance matching. The MnO@N-doped carbon composites achieve an optimal absorption intensity of −62.8 dB at 2.4 mm and a broad effective absorption bandwidth of 5.4 GHz with the thickness of 2.5 mm. The facile synthesis method and the superb EMW absorptivity make the tubular core-shell MnO@N-doped carbon composites a promising EMW absorber, and we believe this study will provide new strategies for designing novel dielectric EMW absorbers in the future. [ABSTRACT FROM AUTHOR]