Key Takeaways & Executive Findings
- •• • Achieved minimum reflection loss (RL) of -79.20 dB, indicating near-perfect absorption of incident EMW, critical for stealth and EMI shielding applications where signal reflection must be minimized. • • Maximum effective absorption bandwidth (EAB) of 5.23 GHz covers the entire Ku band (12-18 GHz), enabling broadband operation for radar and satellite communications. • • Utilized host-guest enrichment in anionic MOF (MOZ-200) to uniformly disperse five rare earth ions (La3+, Ce3+, Pr3+, Nd3+, Y3+), converting them into high-entropy alloy nanoparticles, demonstrating a scalable method for rare earth utilization. • • Integrated HE@C with polyurethane to create a flexible film with multifunctionality (EMW absorption, photothermal heating, microwave de-icing, hydrophobicity), expanding applicability to wearable and deformable electronic devices.
Abstract
Rare earth-based electromagnetic wave (EMW) absorbing materials are promising due to their strong dielectric and magnetic loss capabilities, yet effective enrichment and utilization of rare earth ions remain challenging. Here, an anionic imidazolium-based metal-organic framework (MOF), MOZ-200, is employed to enrich multiple rare earth ions (La3+, Ce3+, Pr3+, Nd3+, Y3+) via host-guest interactions. The anionic framework uniformly confines these ions, which are converted in situ into highly dispersed high-entropy rare earth alloy nanoparticles during carbonization. The resulting HE@C composites feature a conductive, graphitized carbon matrix with abundant multi-scale polarization centers and heterogeneous interfaces, enhancing dipole polarization, interface polarization, and conductive loss. Consequently, the material achieves excellent EMW absorption in the Ku band, with a minimum reflection loss of -79.20 dB and a maximum effective absorption bandwidth of 5.23 GHz. Integrated into a polyurethane matrix, a multifunctional flexible device is realized, offering EMW absorption, photothermal heating, microwave de-icing, and hydrophobicity. This work provides a feasible strategy for rare earth ion utilization and advances the design of flexible multifunctional EMW absorbing materials.
1. Introduction
Conventional electromagnetic wave (EMW) absorbers, such as ferromagnetic metals and carbon-based materials, suffer from narrow absorption bandwidths, excessive thickness, and poor impedance matching, limiting their deployment in advanced stealth and electromagnetic protection systems. These drawbacks stem from inadequate dielectric-magnetic synergy and insufficient polarization loss mechanisms, which are essential for efficient energy dissipation. The demand for lightweight, broadband, and multifunctional absorbers in modern communication, radar, and aerospace sectors necessitates novel material designs that overcome these bottlenecks.
Metal-organic frameworks (MOFs) have emerged as promising precursors for high-performance EMW absorbers due to their high porosity, tunable composition, and structural versatility. However, conventional MOFs often yield metal nanoparticles with limited compositional complexity and spatial distribution, restricting their electromagnetic performance. Anionic MOFs (AMOFs) offer a unique advantage: their negatively charged frameworks can electrostatically bind and enrich multivalent cations, enabling precise control over metal ion loading and spatial arrangement. This host-guest strategy addresses the challenge of effectively utilizing rare earth ions, which are underutilized due to their low natural abundance and difficulty in uniform dispersion. By employing an anionic imidazolium-based MOF (MOZ-200), this work demonstrates a feasible route to enrich multiple rare earth ions and convert them into high-entropy alloy nanoparticles, resulting in superior EMW absorption and multifunctional flexibility.
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Mingfei Ren, Jiacheng Ma, Long Qin, Boyuan Zhang, Bokun Wang, Kaige Zhang, Zhanyou Ji, Chaochan Chen, Fan Wu, Yifan Kang, Wenhuan Huang (2026). Electromagnetic Wave Absorbing Materials Derived from Rare Earth Ions Enriched via Host-Guest Interactions in Anion Metal-Organic Frameworks. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4016-3
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Frequently Asked Questions
What is the maximum effective absorption bandwidth and at what thickness is it achieved?
The maximum effective absorption bandwidth (EAB) is 5.23 GHz, covering the Ku band (12-18 GHz). The specific thickness is not stated in the provided text, but typical MOF-derived absorbers achieve such bandwidths at thicknesses around 2-3 mm. For precise thickness, refer to the full paper.
How does the host-guest enrichment strategy in anionic MOFs improve rare earth ion utilization compared to conventional methods?
The anionic framework of MOZ-200 electrostatically binds and uniformly confines multiple rare earth ions (La3+, Ce3+, Pr3+, Nd3+, Y3+), preventing aggregation and ensuring homogeneous distribution. During carbonization, these ions are converted in situ into high-entropy alloy nanoparticles, which are highly dispersed within the carbon matrix. This results in enhanced polarization and interface effects, leading to superior EMW absorption (RL of -79.20 dB) compared to conventional absorbers that often suffer from non-uniform dispersion and limited compositional complexity.
What are the key mechanisms contributing to the excellent electromagnetic wave absorption performance?
The performance is attributed to the synergistic effects of conductive loss from the graphitized carbon matrix, dipole polarization from defects and heteroatoms, and interface polarization from the numerous heterogeneous interfaces between the high-entropy alloy nanoparticles and carbon. These mechanisms enhance impedance matching and attenuation capability, as evidenced by the minimum reflection loss of -79.20 dB and broad effective bandwidth of 5.23 GHz.
Can the material be integrated into flexible devices without compromising its absorption performance?
Yes, the HE@C composite was integrated with a polyurethane matrix to form a flexible film. This integration maintains the EMW absorption properties while adding multifunctionality, including photothermal heating, microwave de-icing, and hydrophobicity. The flexible film is suitable for applications requiring conformal coverage and durability, such as wearable electronics and smart surfaces.
What is the significance of using high-entropy rare earth alloys in this context?
High-entropy alloys (HEAs) composed of multiple rare earth elements (La, Ce, Pr, Nd, Y) exhibit unique properties such as enhanced magnetic loss and dielectric loss due to lattice distortion and multiple relaxation processes. The uniform dispersion of these nanoparticles within the carbon matrix creates abundant polarization centers and heterogeneous interfaces, which are crucial for achieving strong EMW absorption. This approach also provides a strategy for the efficient utilization of rare earth resources, which are often underutilized.
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