Robust Amino-Functionalized Mesoporous Silica Hollow Spheres Templated by CO₂ Bubbles

Hollow-structured mesoporous silica has wide applications in catalysis and drug delivery due to its high surface area, large hollow space, and short diffusion mesochannels. However, the synthesis of hollow structures usually requires sacrificial templates, leading to increased production costs and environmental problems. Here, for the first time, amino-functionalized mesoporous silica hollow spheres were synthesized by using CO₂ gaseous bubbles as templates. The assembly of anionic surfactants, co-structure directing agents, and inorganic silica precursors around CO₂ bubbles formed the mesoporous silica shells. The hollow silica spheres, 200-400 nm in size with 20-30 nm spherical shell thickness, had abundant amine groups on the surface of the mesopores, indicating excellent applications for CO₂ capture, Knoevenagel condensation reaction, and the controlled release of Drugs.