A porous structure is usually designed to balance impedance matching and attenuation capability of carbon-based microwave absorber, which has been investigated to be an effective way to obtain high microwave absorbing performance, such as strong absorbing capacity and wide effective absorbing bandwidth. Hitherto, there is little known about the suitable value of surface area for such porous structure. In this paper, macroporous C/Co composites were successfully fabricated via in situ carbonization of ZIF-67@SiO2 precursors and subsequent removal of the SiO2 with diameter of similar to 60 nm, and the BET (Brunauer-Emmett-Teller) surface area is optimized by adding amount of SiO2. When the BET surface area is similar to 340 m(2)g(-1), the obtained macroporous C/Co composite shows the best microwave absorbing performance, and the maximum (RL reflection loss) is -56.2 dB with ultra-wide EAB (effective absorbing bandwidth) of 9.0 GHz (9.0-18.0 GHz) at ultralow filler loading of only 10 wt%. (C) 2021 Elsevier Inc. All rights reserved.