• Microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance.

• Outstanding reflection loss value (−62.7 dB), broadband wave absorption (6.4 dB with only 2.1 mm thickness) in combination with flexible adjustment abilities were acquired, which is superior to other relative graded distribution structures.

• This strategy initiates a new method for designing and controlling wave absorber with excellent impedance matching property in practical applications.

In the present paper, a microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance. The inorganic–organic competitive coating strategy was employed, which can effectively adjust the thermodynamic and kinetic reactions of iron ions during the solvothermal process. As a result, Fe nanoparticles can be gradually decreased from the inner side to the surface across the hollow carbon shell. The results reveal that it offers an outstanding reflection loss value in combination with broadband wave absorption and flexible adjustment ability, which is superior to other relative graded distribution structures and satisfied with the requirements of lightweight equipment. In addition, this work elucidates the intrinsic microwave regulation mechanism of the multiscale hybrid electromagnetic wave absorber. The excellent impedance matching and moderate dielectric parameters are exhibited to be the dominative factors for the promotion of microwave absorption performance of the optimized materials. This strategy to prepare gradient-distributed microwave absorbing materials initiates a new way for designing and fabricating wave absorber with excellent impedance matching property in practical applications.

• 为了提高电磁吸收性能，提出了具有纳米级梯度结构的微波吸收体。

• 获得了出色的反射损耗值（−62.7 dB）、宽带吸波（6.4 dB，厚度仅为2.1 mm）以及灵活的调节能力，优于其他相对分级分布结构。

• 该策略开创了一种在实际应用中设计和控制具有优异阻抗匹配特性的吸波器的新方法。

本文提出了一种具有纳米级梯度结构的微波吸收体来增强电磁吸收性能。采用无机-有机竞争涂层策略，可以有效调节铁离子在溶剂热过程中的热力学和动力学反应。结果，Fe纳米颗粒可以穿过中空碳壳从内侧到表面逐渐减少。结果表明，该结构具有优异的反射损耗值，结合宽带吸波能力和灵活的调节能力，优于其他相对分级分布结构，满足设备轻量化的要求。此外，这项工作阐明了多尺度混合电磁波吸收器的固有微波调节机制。优异的阻抗匹配和适中的介电参数是提升优化材料微波吸收性能的主导因素。这种梯度分布吸波材料的制备策略为实际应用中设计和制造具有优异阻抗匹配性能的吸波材料开辟了一条新途径。