Graphitic carbon nitride (g-C3N4) in situ polymerization to synthesize MOF-Co@CNTs as efficient electromagnetic microwave absorption materials

Abstract

Metal-organic framework (MOF) derivatives show potential as electromagnetic microwave (EMW) absorbers. In this study, a series of MOF-Co@CNTs were prepared by pyrolyzing a ZIF-67/g-C3N4 precursor. ZIF-67 catalyzed the polymerization of g-C3N4 into CNTs on the surface of ZIF-67. The effect of the carbonization temperature and ratio of g-C3N4 to ZIF-67 on the EMW absorption capacity of MOF-Co@CNTs is discussed. The complex permittivity increased upon increasing the temperature, but the complex permeability changed only subtly. The optimal process used a carbonization temperature of 700 °C and a mass ratio of g-C3N4 and Co(NO3)2‧6H2O of 1. The RLmin was −59.5 dB at a thickness of 1.6 mm, and the effective bandwidth (RL < −10dB) reached 5.27 GHz at a thickness of 1.8 mm with only 8 wt% filled. Meanwhile, the 99% energy absorption bandwidth (RL < −20dB) reached 13.52 GHz (4.48–18 GHz) at thicknesses from 1.5 to 5.0 mm. Our research provides a new method for introducing CNTs into MOFs by utilizing g-C3N4 as the carbon source, and we believe MOF-Co@CNTs will make excellent EMW absorbers.