Recent developments in the chemical synthesis of inorganic porous capsules

The preparation of hollow inorganic capsules of defined shape, composition and with tailored properties is of immense scientific and technological interest. This article mainly features recent research progress towards various methods for preparing porous inorganic capsules. By choosing some typical inorganic porous capsules as examples, we present a comprehensive overview of synthetic strategies for inorganic capsules, and some typical organic capsules are also included. The available strategies are broadly categorized into three themes, i.e., hard-templating, soft-templating, and template-free routes, and each includes several well-established methods. The current methods show great success in controlling the size, composition, thickness, permeability and function of the finally achieved porous capsules. Applications of porous capsules in biomedicine, energy resources, environment protection and catalysis are also discussed. It is the intention of this contribution to provide a brief account of these research activities.