1D Magnetic Nickel-Carbon Matrix Nanotube Composites Derived from Hydrogen-Bonded Organic Frameworks and Metal–Organic Frameworks for Electromagnetic Wave Absorption

Hydrogen-bonded organic frameworks (HOFs) and metal–organic frameworks (MOFs) emerge as promising materials for electromagnetic wave (EMW) absorption, due to their high specific surface area and readily modifiable characteristics. In this study, 1D magnetic nickel-carbon matrix nanotube composites (Ni-HMCNTs) from a mixture of HOFs and MOFs (Ni-HMNTs) for EMW absorption are synthesized. The Ni-HMNTs are achieved via a one-step method involving a single-pot solvothermal reaction among melamine, trimeric acid, and nickel nitrate. This process involves a HOF-to-MOF transformation, characterized by the penetration of Ni ions into the HOF structure via a competitive coordination reaction, resulting in the hollow structure of Ni-HMNTs. Subsequent calcination of Ni-HMNTs yields Ni-HMCNTs optimized for EMW absorption. Remarkably, with a filling degree of only 10 wt%, 1.2 Ni-HMCNTs-700 (heat-treated at 700 °C) exhibits exceptional EMW absorption properties, with a minimum reflection loss (RL_min) value of −50.4 dB and a maximum effective absorption bandwidth (EAB) of 7.32 GHz (10.64–17.96 GHz). These findings pave the way for further exploration of magnetically modified HOFs/MOFs for EMW applications.