Tunable Structural Colors with ‘Light‐Lossy’ MXene Paints

Thin‐film interference with a Fabry–Pérot cavity is a classic approach to generating structural colors for anti‐counterfeiting, sensors, and aesthetical demands. However, an absorbing layer capable of balancing the reflectance and absorption bands remains elusive, thereby limiting the chromatic and luminant tunability of structural coloration. Here wide‐color‐gamut films are reported with MXene as the absorbing layer in a simple trilayer configuration for vivid structural colors, outperforming conventional metal‐ and semiconductor‐based films. It is demonstrated that the ‘lossy’ refractive indices of different metallic MXene compositions broaden the absorption bandwidth of multilayer films and maintain the high reflectance, enabling a substantial and complementary gamut with high tunability beyond the area of sRGB color space. Various structural color films/patterns based on MXenes showcase the compatibility for different scenarios. The results accompanied by theoretical calculations provide insights into the fundamental understanding of light‐MXene interaction in coloration. The unique optical absorbance and solution processibility of the MXene family offer a versatile platform for the physical manipulation of light beyond conventional manufacturing approaches.