Beyond reflection: thickness-guided engineering of MXenes for green electromagnetic shielding

Rapid advancement of 5G/6G communication technologies has not only driven a paradigm shift in telecommunication systems, but also caused escalating electromagnetic (EM) pollution, which threatens the reliability of radio frequency (RF) devices and human health. Conventional EM shielding materials rely on reflection-dominated mechanisms enabled by high conductivity, which cause secondary EM pollution and conflict with sustainable development goals. Consequently, green EM shielding, emphasizing absorption-dominated attenuation with suppressed reflection, has emerged as a critical research direction. MXenes, a class of 2D transition metal carbides and nitrides, have attracted considerable attention for green EM shielding due to their high conductivity, layered architecture, tunable surface terminations, and solution processability. This review summarizes recent advances in MXene-based green EM shielding, focusing on shielding mechanisms, evaluation metrics, and thickness-dependent design principles. By distinguishing thin/ultrathin from thick shielding structures, we analyze intrinsic MXene regulation, interfacial engineering, composite architectures, and 3D designs that enhance impedance matching and promote absorption-dominated behavior. Synergistic contributions of conduction loss, dielectric/interfacial polarization, magnetic loss, and multiple reflections are discussed, alongside the applicability and limitations of the green shielding index (g_s). Finally, current challenges and future prospects are highlighted, including the performance trade-offs across frequency bands and underutilization of intrinsic MXene properties.