Nanocrystalline titanium dioxide $(TiO_2)$ not only has been widely used in industrial applications, such as photocatalysis, and sensor, owing to its high photoactivity and chemical stability, but also has attracted much attention as an effective support for metal nanoparticles due to its strong metal-support interaction. The versatile applicability of the nanocrystalline $TiO_2$ is attributed to the increase of active metal surface area and the formation of pores existing between the nanocrystals, which promote a facile diffusion of reactants. In this thesis, a synthetic strategy is proposed to effectively design $TiO_2$ nanostructures with high applicability by using a random copolymer of 4-vinylphenol and methyl mathacrylate as a structure-directing agent. In this method, $TiO_2$ nanosponge with uniform mesopores and sub-nanometer thick $TiO_2$ nanosheet could be readily synthesized by changing the synthesis composition. Thus, it is possible to design the $TiO_2$ nanostructures in the appropriate form depending on necessity, by controlling crystal thickness and porosity of $TiO_2$ nanostructures. Moreover, the catalytic applicability of $TiO_2$ nanostructure has been proposed, as Pt nanoparticles (NPs) supported on mesoporous $TiO_2$ exhibited the high dispersion of the Pt NPs.