Metal-organic framework derived hollow CoFe@C composites by the tunable chemical composition for efficient microwave absorption.

Controlling the composition and microstructure of nanomaterials is still a significant challenge in developing high-performance microwave absorption (MA) materials. Herein, metal-organic framework (MOF)-derived hollow CoFe@C nanoboxes are designed and prepared through the facile regulating the mass ratios of ZIF-67/PFC and a thermal annealing treatment. The CoFe@C composite can achieve an excellent MA performance, which have two high reflection loss (RL) values at different thickness. A RL value of -31.0 dB is obtained at 11.84 GHz with a matching thickness of 2.4 mm, and a RL value can reach -44.1 dB (4.08 GHz) at a matching thickness of 5.8 mm, and a correspondingly wide absorbing bandwidth (5.20 GHz, from 9.7 to 14.9 GHz) is simultaneously obtained at a matching thickness of 2.3 mm. The magnetic loss, interfacial polarization and hollow structure are the main reasons for their excellent MA capability. This work provides a research idea for the development of the efficient MOF-based MA materials in practical application.