Unidirectional Evaporation-Induced Tunable and Continuous Gradient Composite Structure for Absorption-Dominant...

Absorption-dominant electromagnetic interference (EMI) shielding requires simultaneous control of electrical conductivity and impedance matching to suppress secondary electromagnetic pollution. Here, we report a facile, scalable unidirectional evaporation method to fabricate MXene-decorated melamine foams with a continuous, tunable electrical conductivity gradient across the thickness, free of discrete layer boundaries. Directional solvent evaporation induces controlled redistribution of MXene nanosheets within the three-dimensional porous framework, governed by the synergistic effects of capillary, gravity, and Marangoni forces. By systematically tuning evaporation parameters, including temperature, humidity, and MXene concentration, the gradient profile can be regulated to optimize impedance matching and electromagnetic wave attenuation. The resulting composite exhibits outstanding absorption-dominant EMI shielding performance, delivering a stable total shielding effectiveness of 53.84 dB across the X-band with an ultralow reflection shielding effectiveness of 0.032 dB, corresponding to a high absorptivity of 0.99276. This work provides a general pathway for constructing continuous-gradient architectures in porous composites, offering new opportunities for designing high-performance, low-reflection EMI shielding materials.