Hollow Engineering to Co@N‐Doped Carbon Nanocages via Synergistic Protecting‐Etching Strategy for Ultrahigh Microwave Absorption

Abstract

Rational manipulation of hollow structure with uniform heterojunctions is evolving as an effective approach to meet the lightweight and high‐performance microwave absorption for metal‐organic frameworks (MOFs) derived absorbers. Herein, a new and controlled synergistic protecting‐etching strategy is proposed to construct shelled ZIF‐67 rhombic dodecahedral cages using tannic acid under theoretical guidance, then hollow Co@N‐doped carbon nanocages with uniform heterojunctions and hierarchical micro‐meso‐macropores are obtained via a pyrolysis process, which addresses the shortcomings of using sacrificing templates or corrosive agents. The outer Co@N‐doped carbon shell, composed of highly dispersive core‐shell heterojunctions, possesses micro‐mesopores while the inner hollow macroporous cavity endows the absorbers with lightweight characteristics. Accordingly, the maximum reflection loss is −60.6 dB at 2.4 mm and the absorption bandwidth reaches 5.1 GHz at 1.9 mm with 10 wt% filler loading, exhibiting superior specific reflection loss compared with the vast majority of previous MOFs derived absorbers. Furthermore, this synergistic protecting‐etching strategy provides inspiration for precisely creating a hollow void inside other MOFs crystals and broadens the desirable candidates for lightweight and high‐efficient microwave absorbers.

Flexible and Waterproof 2D/1D/0D Construction of MXene-Based Nanocomposites for Electromagnetic Wave Absorption, EMI Shielding, and Photothermal Conversion

“…In addition, substantial development of electromagnetic wave absorption and EMI shielding was achieved for MXene-based composites with a novel structure. Examples included hollow structures [32][33][34][35], porous structures [36,37,2], and layer structures [38,39]. The laminated porous structure gives the material the advantages of a lightweight, abundant interfacial polarization, and multiple scattering and reflection, which can attenuate more electromagnetic wave energy [40][41][42].…”

3D Seed-Germination-Like MXene with In Situ Growing CNTs/Ni Heterojunction for Enhanced Microwave Absorption via Polarization and Magnetization

“…Microwave absorption (MA) materials are highly demanded in many areas of 5G high-frequency communication, wireless systems, military stealth, and prevention of electromagnetic (EM) wave interference & pollution [1][2][3][4][5]. Conventionally, a superior MA absorber depends mainly on a satisfied impedance condition (Z value) and a distinct EM attenuate capability (α value) that composed of polarization [6,7], conductive [8,9], and magnetic loss [10,11].…”

Tuning Dielectric Loss of SiO2@CNTs for Electromagnetic Wave Absorption

“…As shown in Figure S8, multiple Cole-Cole semicircles could be found in the curve of the SiO 2 @Fe 3 C/Fe@NCNT-GT, confirming the existence of dipole polarization and interfacial polarization relaxation. Therefore, the increased dielectric relaxation loss of the SiO 2 @Fe 3 C/Fe@NCNT-GT is relevant to their enhanced dipole and interface polarizations [31][32][33][34][35]. Figure 5 shows the R L -f curves of the two samples with d of 1.5-5.0 mm over 2-18 GHz.…”