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 CoTiO 3 as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °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 NiTiO . Those novel materials make it possible to build up correlations between mesoscale porosity and surfacesensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO 3 , 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.complex oxides, in general, has associated kinetic barriers from the slow diffusion in solids. [15] When there are two metal cations involved in crystallization of complex oxides like ABO 3 , their nonuniform distribution can result in spontaneous phase separation to form simple oxides. [16] A delicate balance of their sol-gel rates and the precautious control of thermal annealing procedure is needed. On the other hand, ordering competition between the crystallization of oxides and the mesoscale porosity brings profound difficulties to synthesize complex oxides (e.g., perovskites and ilmenites) with mesoporous structures. Crystallization usually leads to the formation of large crystalline grains that will create strong interfacial energies between crystalline walls and pores (e.g., air or templates). For any templated growth of mesoporous oxides using hydrocarbon-based surfactants or block copolymers (BCPs) as soft templates, [17][18][19] mesoscale nanostructures collapse prior to the crystallization of oxides, [20][21][22] because these soft templates are not mechanically strong and thermally stable under elevated temperatures (i.e., >500 °C).Nanostructures show a profound impact on the magnetic properties of materials as well and a few theoretical models have been proposed to understand magnetic behavior of nanoscale particles. [23][24][25][26][27][28][29][30] The magnetic ordering temperature (Curie temperature or Néel temperature) in magnetic materials