Coupled metal-node and chalcogen modulation in pristine 2D conjugated MOFs for carbonization-free electromagnetic wave absorption

Electromagnetic interference (EMI) generated by densely deployed wireless electronics calls for lightweight absorbers that can simultaneously deliver strong attenuation and good impedance matching over broad frequency windows. Metal-organic frameworks (MOFs) are structurally programmable, yet most high-performance MOF absorbers rely on high-temperature carbonization, which obscures the intrinsic structure-property relationship of pristine frameworks. Here we propose a carbonization-free strategy using two-dimensional conjugated MOFs (2D c-MOFs) in which both the metal nodes (M = Cu, Zn, Co, Ni) and chalcogen functionalities (X = S, Se) are jointly engineered within an isostructural M-XHHTP family. The resulting materials form extended, electrically percolative frameworks with abundant polarization sites, facilitating an improved balance between dielectric loss and impedance matching. Among the series, Cu-Se₃HHTP exhibits the best microwave-absorption performance, delivering a minimum reflection loss (RL_min) of −24.20 dB at 80 wt% loading and achieving a maximum effective absorption bandwidth (RL < −10 dB) of 6.08 GHz (matched thickness 2.11 mm). Notably, the absorption can be shifted toward low-frequency operation, and Cu-Se₃HHTP shows an RL_min of −24.20 dB in the 4–6 GHz at a thickness of 5.0 mm. This work demonstrates pristine 2D c-MOFs as efficient, tunable electromagnetic wave (EMW) absorbers and provides a design guideline for triphenylene-based frameworks via coupled metal-node/chalcogen modulation.