MOF-on-MOF-Derived CeO₂/Fe@C Composites for Tunable Low-Frequency Electromagnetic Wave Absorption

Area of Science:

• Materials Science
• Nanotechnology
• Electromagnetics

Background:

• Designing low-frequency (2-8 GHz) electromagnetic wave (EMW) absorbing materials is crucial but challenging.
• Controlled low-frequency absorption window migration in materials is a significant hurdle.

Purpose of the Study:

• To develop a novel strategy for fabricating efficient low-frequency EMW absorbers.
• To investigate the effect of temperature-programmed pyrolysis on MOF-derived composites for EMW absorption.

Main Methods:

• In situ growth of a MOF-on-MOF precursor (UiO-66@MIL-88B).
• Temperature-programmed pyrolysis to convert the precursor into CeO2/Fe@C (CFC) composites.
• Characterization of EMW absorption performance, including reflection loss (RL) and effective absorption bandwidth (EAB).

Main Results:

• Optimized CFC-2 achieved a minimum RL of -62.20 dB at 7.84 GHz with an EAB of 5.36 GHz at 1.70 mm thickness.
• Increasing pyrolysis temperature shifted optimal absorption to lower frequencies, with CFC-3 reaching -42.54 dB at 4.00 GHz.
• CFC composites exhibited superior low-frequency performance compared to Fe@C and CeO2@C, attributed to abundant interfaces, defect-rich carbon, and oxygen vacancies.

Conclusions:

• The MOF-on-MOF derived CeO2/Fe@C composites offer a promising route for low-frequency EMW absorption.
• Temperature-programmed regulation is key to tuning the absorption performance and shifting the absorption window to lower frequencies.
• The synergistic effects of multi-scale interfacial polarization and magnetic loss contribute to enhanced EMW attenuation and impedance matching.