Ultralight and high-elastic carbon foam with hollow framework for dynamically tunable electromagnetic interference shielding at gigahertz frequency

Electromagnetic interference (EMI) shielding materials with lightweight and tunability are highly desirable for practical applications in complex environments. Carbon-based materials as EMI materials are lightweight and highly environment-friendly, but generally rigid. Herein, we demonstrate novel nitrogenous carbon foams (NCFs) with the hollow framework, possessing multiple merits of ultralight, ultraelasticity and proper electrical conductivity. Such a significant architecture thus results in an excellent EMI shielding performance. Experimental characterizations combining with the first principle calculations indicate that the origins of microwave absorption and shielding characteristics are ascribed to the atomic-scale nitrogen substitutions in carbon matrix, which induce the structural symmetry breaking and the re-distribution of localized charge, forming a high density of electric dipoles. By compressing/releasing the NCFs, the electromagnetic (EM) performance can be arbitrarily tuned due to the phase cancellation within the three-dimensional foam structure and the tunable conductivity. The present work has important implications in understanding the intrinsic origin of strengthening EM radiation, and meanwhile provides a strategy for the design of “dynamic” EM functional materials.