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

Abstract

electromagnetic energy conversion workstations" presents a viable approach to address the above challenge, which requires the development of high-performance microwave absorbing (MA) materials. [1][2][3] Metal-organic frames (MOFs), constructed from potential metal units (e.g., Fe, [4] Co, [5] and Ni [6] ) and organic ligand, are possible idea candidates due to the dazzling collocation, easy-to-lock dielectric/magnetic combination, [7,8] as well as favorable electromagnetic coordination and attenuation. [9][10][11] At present, increasingly stringent performance indicators, such as wide electromagnetic absorption bandwidth (EAB >7 GHz), limit the promotion of MOFs. Fortunately, the micro-engineering of such MOFs with cavities, such as yolk-shell, [12][13][14] macroporous, [15,16] and especially hollow, [17,18] has been demonstrated to reduce the density, suppress eddy current, and improve impedance matching. [19] However, traditional hollow routes, such as the external template methods (e.g., SiO 2 , polystyrene, etc.), [20] have been revealed to be time-consuming, complex, and acid-base corrosion. [21,22] Zeolite imidazole frame-67 (ZIF-67) has been the most studied template, in which Co 2+ ions are connected to imidazole 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 Ni 2+ -exchange strategy is proposed to synthesize graphite/CoNi alloy hollow porous composites from Ni 2+ 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.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202200429.

Facile synthesis of ZIF-67 derived dodecahedral C/NiCO2S4 with broadband microwave absorption performance

“…In order to distinguish which loss mechanism is dominant in the high frequency bands, it is generally demonstrated by plotting the eddy current loss coefficient C 0 curve. The expression for C 0 is as follows: 61–63 C 0 = μ ′′( μ ′) −2 f −1 = 2π μ 0 d 2 σ if the magnetic loss of the sample is all due to eddy current loss in a certain frequency band, the C 0 curve in this frequency band should be a straight line, which represents that the slope of C 0 curve is a constant. By observing and analyzing the C 0 curves of each sample in Fig.…”

“…In order to distinguish which loss mechanism is dominant in the high frequency bands, it is generally demonstrated by plotting the eddy current loss coefficient C 0 curve. The expression for C 0 is as follows: [61][62][63]…”

Catfish Effect Induced by Anion Sequential Doping for Microwave Absorption

“…These defects can entirely trigger high-energy unsaturated sites, inducing the formation of electric dipoles to promote electromagnetic energy dissipation. [44,45]…”

Review and Perspective of Tailorable Metal‐Organic Framework for Enhancing Microwave Absorption

“…The ultra‐ EAB value of 7.63 GHz with a loading of 24 wt% and an RL min of –63.79 dB with a loading of 20 wt% were achieved via adjusting cavity enhancing impedance matching. [ 29 ]…”

“…Furthermore, the controllable microstructural and chemical composition design of the MOF‐precursors has aroused extensive attention in preparing high‐performance MAMs. More importantly, the burgeoning conductive MOFs have become a crucial option in manufacturing efficient MAMs with multifunction, [ 27‐28 ] lightweight, [ 29‐30 ] and low‐frequency absorption. [ 31‐32 ]…”