A hollow CuS@Mn(OH)2 particle with double-shell structure for Ultra-wide band electromagnetic absorption

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.

Fabrication of bimetallic metal-organic frameworks derived cobalt iron alloy@carbon-carbon nanotubes composites as ultrathin and high-efficiency microwave absorbers

Developing lightweight and high-efficiency microwave absorbents derived from metal-organic frameworks (MOFs) was proven to be a promising strategy to solve the increasingly serious problem of electromagnetic radiation pollution. In this work, nitrogen-doped cobalt iron alloy@carbon-carbon nanotubes (CoFe alloy@C-CNTs) composites were fabricated through an aging and pyrolysis two-step method. Results revealed that the attained composites presented a unique four-pointed star morphology and lots of CoFe alloy nanoparticles were uniformly embedded into the porous carbon matrix. Moreover, it was found that the pyrolysis temperature had a notable effect on the microwave absorption properties of CoFe alloy@C-CNTs composites. Remarkably, the obtained composite under 700.0 °C pyrolysis treatment showed the optimal minimum reflection loss of -54.5 dB with an ultrathin thickness of 1.4 mm and maximum effective absorption bandwidth of 5.0 GHz at a low thickness of 1.6 mm. Additionally, the possible electromagnetic attenuation loss mechanisms of attained composites were illuminated. It was believed that our results could be helpful for fabricating ultrathin and high-performance microwave absorbing materials derived from MOFs.

Enhanced Electromagnetic Wave Absorption Properties of Ultrathin MnO2 Nanosheet-Decorated Spherical Flower-Shaped Carbonyl Iron Powder

In this work, spherical flower-shaped composite carbonyl iron powder@MnO₂ (CIP@MnO₂) with CIP as the core and ultrathin MnO₂ nanosheets as the shell was successfully prepared by a simple redox reaction to improve oxidation resistance and electromagnetic wave absorption properties. The microwave-absorbing properties of CIP@MnO₂ composites with different filling ratios (mass fractions of 20%, 40%, and 60% after mixing with paraffin) were tested and analyzed. The experimental results show that compared with pure CIP, the CIP@MnO₂ composites have smaller minimum reflection loss and a wider effective absorption bandwidth than CIP (RL < -20 dB). The sample filled with 40 wt% has the best comprehensive performance, the minimum reflection loss is -63.87 dB at 6.32 GHz, and the effective absorption bandwidth (RL < -20 dB) reaches 7.28 GHz in the range of 5.92 GHz-9.28 GHz and 11.2 GHz-15.12 GHz, which covers most C and X bands. Such excellent microwave absorption performance of the spherical flower-like CIP@MnO₂ composites is attributed to the combined effect of multiple beneficial components and the electromagnetic attenuation ability generated by the special spherical flower-like structure. Furthermore, this spherical flower-like core-shell shape aids in the creation of discontinuous networks, which improve microwave incidence dispersion, polarize more interfacial charges, and allow electromagnetic wave absorption. In theory, this research could lead to a simple and efficient process for producing spherical flower-shaped CIP@MnO₂ composites with high absorption, a wide band, and oxidation resistance for a wide range of applications.