Hollow Core-Shell Bismuth Based Al-Doped Silica Materials for Powerful Co-Sequestration of Radioactive I₂ and CH₃I

Developing pure inorganic materials capable of efficiently co-removing radioactive I₂ and CH₃I has always been a major challenge. Bismuth-based materials (BBMs) have garnered considerable attention due to their impressive I₂ sorption capacity at high-temperature and cost-effectiveness. However, solely relying on bismuth components falls short in effectively removing CH₃I and has not been systematically studied. Herein, a series of hollow mesoporous core-shell bifunctional materials with adjustable shell thickness and Si/Al ratio by using silica-coated Bi₂O₃ as a hard template and through simple alkaline-etching and CTAB-assisted surface coassembly methods (Bi@Al/SiO₂) is successfully synthesized. By meticulously controlling the thickness of the shell layer and precisely tuning of the Si/Al ratio composition, the synthesis of BBMs capable of co-removing radioactive I₂ and CH₃I for the first time, demonstrating remarkable sorption capacities of 533.1 and 421.5 mg g^-1, respectively is achieved. Both experimental and theoretical calculations indicate that the incorporation of acid sites within the shell layer is a key factor in achieving effective CH₃I sorption. This innovative structural design of sorbent enables exceptional co-removal capabilities for both I₂ and CH₃I. Furthermore, the core-shell structure enhances the retention of captured iodine within the sorbents, which may further prevent potential leakage.