Fabrication of core-shell nanoporous carbon@chiral polyschiff base iron(II) composites for high-performance electromagnetic wave attenuationin the low-frequency

Highlights: • Unique core-shell NPC@CPI was synthesized via In-Situ coating.• Attenuation ability was improved greatly due to the synergistic effect of NPC&CPI.• The optimal RL was -60.8 dB at the low-frequency of 3.89 GHz.• The effective bandwidth of 5.6 GHz (RL less than -10 dB) was achieved at 1.65mm. -- Abstract: A key aspect of refining the design and manufacture of contemporary microwave absorbing materials is to improve their absorption of electromagnetic radiation at low frequency which has proved to be an immensely challenging task. This work reports a relatively uncomplicated method to design core-shell absorbers through nanoporous carbon (NPC) obtained by removing redundant Cu from the pyrolysis products of HKUST-1 (HKUST is the Hong Kong University of Science and Technology) coated with (1R,2R)-(−)-1,2-cyclohexanediamineferrocene formaldehyde polyschiff base iron (II) (CPI). Three NPC@CPI samples not only maintain good impedance matching of the pyrolysis products of HKUST-1, but also increase the attenuation abilities significantly due to the synergetic effect of multiple interfacial polarization, cross-polarization and Debye relaxation, which further leads to their outstanding microwave absorbing performance. When the mass ratio of CPI to NPC is 6.7:100 (NPC@CPI-1), the strongest reflection loss (RL) can achieve −60.8 dB at 3.7 GHz, whereas the RL bandwidth under −10 dB can become as much as 5.6 GHz at 1.65 mm. While CPI to NPC is 10:100 (NPC@CPI-2), an optimal RL of −46.9 dB at 11.7 GHz and 1.9 mm can be achieved. This work thus provides an excellent model for the design and the manufacture of thin, lightweight, broad, and strong EM absorbers based on MOFs derivatives and chiral polymers.