Photon‐Cage‐Structured Aerogels with Quadruple Complementary Compounds for Efficient X‐Ray Absorption

Abstract Traditional lead‐based materials are becoming increasingly inadequate for advanced radiation protection. The development of high‐performance lead‐free shielding materials is essential to promote the safer and more efficient use of X‐rays. In this study, the effect of the complementary K‐edges of Cs 3 Bi 2 I 9 and Gd on X‐ray absorption is investigated. Gd is strategically incorporated into an aerogel through a phase‐separation strategy to form a unique “photon‐cage” structure. Subsequently, polydimethylsiloxane encapsulation provides the aerogels with excellent mechanical properties and thermal stability. Finally, Cs 3 Bi 2 I 9 nanomaterials are introduced to produce a photon‐cage‐structured X‐ray‐shielding aerogel. This structure effectively prolongs photon residence time and promotes multiple internal scattering events, thereby effectively trapping and absorbing X‐ray photons. The fabricated aerogels exhibit excellent X‐ray shielding efficiencies, ranging from 76.4 to 97.3% in the 40–120 kV energy range. These findings offer a promising pathway for the development of flexible, high‐efficiency, and lead‐free X‐ray‐shielding materials.