Nanoimprint lithography (NIL) is nowadays the most popular and effective method to develop new environmentally-friendly and low-cost photonic nanodevices. Combined with titanium dioxide (TiO2) in the form of sol-gel, photonic nanostructures with low absorption and high refractive index can be produced, which can be of interest for many applications for which sustainability becomes increasingly important. In this paper, we present a patterning process based on soft NIL of TiO2 sol-gel, and show that the very good pattern transfer has been obtained, which can be completed with independence from the feature size, shape and height of the patterns. We also propose a low-temperature (400°C) calcination process rather than 450°C or higher temperature to crystallize the TiO2 nanostructures, which leads to very similar crystalline structures to higher-temperature processes, and a vertical shrinkage of about 61% compared to the imprinted pattern. Using this environmentally-friendly combined soft-NIL + calcination process, we show that submicron patterns with heights above 300 nm can be obtained. Such a large pattern height, combined with the wide range of pattern shapes and dimensions that can be fabricated, opens the possibility of a wide diversity of designs for the eco-friendly fabrication of TiO2 nanostructures with highly-interesting photonic properties.