Hierarchically patterned macroporous TiO2 structures can be fabricated via the spontaneous self-assembly of TiO2 nanoparticles prepared using a mixture of 1-octadecene (ODE) and an ODE-immiscible 1-alkyl-3-methylimidazolium-based ionic liquid as the reaction medium. A study of the influence of side chain lengths of ionic liquids (n=4, 8, or 16) reveals that this parameter can be further used to fine-tune the morphologies of the products. This synthetic methodology can also be extended to the formation of patterned macroporous ZrO2 and Fe3O4 structures. Finally, the potential reasons for the formation of hierarchical structures are discussed and the implications to further research are proposed.