General Surface-Casting Synthesis of Mesoporous Metal Oxides with Hollow Structures and Ultrahigh Surface Areas

Metal oxides with high specific surface areas have essential roles in numerous applications. Over the past decades, various efforts to increase their surface areas have been made. One of the most important ways is to create nanopores inside the solids, resulting in mesoporous materials. However, ordered mesoporous metal oxides with crystalline framework, regular arrangement of pores, and very high surface areas have scarcely been achieved due to structural collapse during the high-temperature treatment. Herein, a family of mesoporous metal oxides with crystalline framework, hollow mesostructure, and ultrahigh surface area is synthesized by a surface-casting method. The strong interaction between the silica template surface and the precursors is vital in the formation of a thin layer of metal oxides on the nanopore surface. Metal oxides with tubular, hollow sphere, or hollow vesicle structures can be obtained after the templates are removed. The obtained surface-cast oxides (SCOs), including ZrO2, Fe2O3, CrOx, TiO2, and others, exhibit ultrahigh surface areas of up to 400 m2 g–1. The high surface area feature of the SCO material can even be retained after calcination up to 800 °C. Catalytic tests reveal that the SCO materials with more exposed active sites have better activities than their conventional counterparts.