Pearson's principle inspired generalized strategy for the fabrication of metal hydroxide and oxide nanocages

Designing a general route for rational synthesis of a series or families of nanomaterials for emerging applications has become more and more fascinating and vital in the view of nanoscience and nanotechnology. Herein, we explore a general strategy for fabricating uniform nanocages of metal hydroxides (MHs) and metal oxides (MOs). A template-assisted route inspired by Pearson's hard and soft acid-base (HSAB) principle was employed for synthesizing MH nanocages via meticulous selection of the coordinating etchant as well as optimization of the reaction conditions. The concept of "coordinating etching" is successfully achieved in this work. This unique route shows potential in designing well-defined and high-quality MH nanocages with varying components, shell thicknesses, shapes, and sizes at room temperature. Consequently, porous MO nanocages can be obtained readily just through appropriate thermal treament of the respective MH nanocages. The overall strategy present in this work extends the application of the HSAB principle in nanoscience and offers a unqiue clue for rational fabrication of hollow (porous) and/or amorphous structures on the nanoscale, where these nanocages may present promising potential for various applications.