Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m²  g^-1 . We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell-supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO₂ ), transition metal (Ni/SiO₂ ), metal oxide (CrO₃ /SiO₂ ), and alumina support (Co/Al₂ O₃ ). As a prototypical application, we perform dry reforming of methane using Ni/SiO₂ , achieving constant 97 % CH₄ and CO₂ conversions for more than 200 hours, dramatically outperforming an MCM-41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.