Transition metal carbon composites derived from metal organic frameworks (MOFs) attract increasing attention in microwave absorption field. However, finding a relatively facile and green method to prepare MOFs precursor is still a challenge. Besides, it is also difficult to obtain carbon nanotubes based compounds by only using MOF as sacrificed template. Herein, nickel (Ni) MOF is fabricated at room temperature with water as solvent. Afterwards, nickel/carbon nanotubes composite (Ni/CN) is prepared via only in-situ pyrolysis of Ni MOF. The pyrolysis temperature greatly affects nitrogen (N) dopant state for Ni/CN composites. The Ni/CN composite prepared at 700 degrees C (Ni/CN-700) exhibits the maximum reflection loss (RL) of-65 dB with the effective absorbing bandwidth (EAB) about 4.6 GHz at 1.9 mm, when the filling loading is only 10 wt% in the matrix. Remarkably, the Ni/CN composite is excellent microwave absorber with lightweight and strong absorption. The magnetic metal/carbon nanotubes derived from MOF prepared in green solvent offers a facile, environmentally friendly and designable strategy for exploring excellent microwave absorber. (c) 2021 Elsevier Inc. All rights reserved.