Hierarchical architectures TiO2: Pollen-inducted synthesis, remarkable crystalline-phase stability, tunable size, and reused photo-catalysis

► The synthetic method is much milder and simpler than that of conventional methods. ► The obtained hierarchical TiO2 shows three interesting hierarchical morphology. ► The products have tunable crystal phase structures. ► The pure phase of anatase can be retained after being annealed at 900 °C. ► The product exhibits higher and reused photo-catalytic activity.