Advanced electromagnetic (EM) wave absorbing materials containing both magnetic and dielectric components have attracted considerable attention for the ever-developing electronic and telecommunication devices. It is however, rather challenging to combat the sacrificed magnetic loss due to magnetic dilution by the introduction of the dielectric component. Here a novel confinement strategy has been adopted to develop porous heterogeneous Fe7Co3/ZnO nanosheets where Fe7Co3 nanoparticles with single domain size and dispersed distribution can be achieved for enhanced natural resonance. The nanosheets exhibit unique porous feature with significantly reduced density. Also, tunable dielectric loss achieved via interruption of the Fe7Co3 conducive network functions synergistically with the magnetic loss for enhanced absorption over a wide frequency range (7.92 GHz), covering the complete Ku band and half of the X band. The confinement strategy proposed in this study not only paves the way for designing high-performance EM wave absorber with low density and broad bandwidth, but also provides a versatile method for the synthesis of two-dimensional composites with tunable composition for extended applications in energy storage, catalysis, biomedicine and sensing.