Dimensionality-regulated Hofmann MOF-derived 3D core–shell CoNi/C composites for high-performance broadband microwave absorption

Abstract

The intrinsic structural limitations of two-dimensional (2D) materials often lead to impedance mismatch, limited absorption bandwidth, and pore collapse during high-temperature carbonization, severely restricting their microwave absorption performance. Herein, a dimensional regulation strategy to go from 2D to three-dimensional (3D) architectures is proposed. By introducing 4,4′-bipyridine as a pillar ligand, a 2D Co[Ni(CN)₄] Hofmann MOF is transformed into a 3D framework with interconnected pore channels. After carbonization, a porous CoNi/C composite (Hofmann-X) is obtained, featuring high specific surface area, abundant micro/mesopores, and uniformly dispersed metal nanoparticles. The 3D architecture significantly enhances interfacial polarization and optimizes electromagnetic parameter matching, leading to synergistic dielectric–magnetic loss. As a result, the optimized absorber delivers a minimum reflection loss (RL_min) of −59.4 dB at a thickness of 2.1 mm and an effective absorption bandwidth (EAB) of 8.04 GHz. This work provides a new strategy for enhancing broadband microwave absorption performance of MOF-derived materials through structural dimensional regulation.