Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response

A colloidal-amphiphile-templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane-containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO3 as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 degrees C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO3, FeTiO3, ZnTiO3, Co2TiO4, Zn2TiO4, MgTi2O5, and FeTi2O5. Those novel materials make it possible to build up correlations between mesoscale porosity and surface-sensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO3, there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.