We herein report a large-scale synthesis of hierarchically porous TiO2 structures composed of nanoparticles by a facile soft-template method. The natural and abundant biopolymer named alginate acted as sacrificial templates, providing porous structures and controlling the morphology of TiO2 nanoparticles. The size of the resultant TiO2 nanoparticles was around 20 nm. The TiO2 structures were obtained by directly crosslinking Ti4+ ions to alginate and then burning off the biopolymer templates. Based on the observation of various reactive conditions, we propose that the alginate has two important function in the formation of hierarchically porous TiO2 structures. One is acting as a template for the nucleation of TiO2. The other one is to facilitate the formation of porous TiO2 nanomaterials. The photocatalytic property of hierarchically porous TiO2 in UV-light-driven degradation of organic dyes was proved to be better than that of commercial available TiO2. (C) 2016 Elsevier Ltd. All rights reserved.