Alkali and Co²⁺ co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing (MA) materials. In this work, a new alkali and Co ion exchange co-modulation strategy was first reported, leading to broadband MA capacity through simultaneous manipulating multiple factors, such as composition, micromorphology, and heterogeneous interface. And enhancements in impedance matching and magnetic–dielectric loss were synergistically realized. Consequently, the optimized FeCo alloy@porous carbon (FPC) nanocomposite with the alkali regulation delivered an effective absorption bandwidth (EAB) of 6.72 GHz, making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%. Interestingly, the nanocomposites by ion exchange strategy realized the switchable “on/off” states on electromagnetic response. Furthermore, the radar cross-section (RCS) reduction value of the products reached 25.6 dB·m² under the incident angle of 0°. In brief, this work not only offers the special role of alkali and Co²⁺ co-modulation in composition regulation, structure design, and MA capacity, but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.