Tailoring anisotropic ZnO/wood-structural holocellulose hybrids for dye degradation through controlled nanoinsertion

Nanostructured inorganic/wood-structural holocellulose hybrids offer new potential applications, including mechanical energy conversion, superhydrophobic materials, gas adsorption and so on. Owing to the anisotropy of wood, controlling the morphology of mineral particles inside porous holocellulose scaffold is still far from satisfactory. In this work, a homogeneous zinc oxide (ZnO) decoration inside wood-structural holocellulose scaffold was achieved while the morphology, distribution and content of ZnO micro-nano particles were controllable through changing the conditions of hydrothermal growth. The holocellulose scaffold was prepared through delignification and periodate oxidation, which is favorable for Zn²⁺ capture and ZnO nuclei formation because of the surface charge increased. The controlled ZnO insertion was realized by changing metal salt concentration, temperature and hydrothermal time. The obtained multilayer ZnO could provide multiple light refractions and reflections and enhance the utilization of light. Consequently, with a minor ZnO loading (15 wt%), the ZnO/wood-structural hybrids could totally degrade methyl orange and methyl blue in 6 h. This novel and scalable synthesis method shows potential for both the design and photocatalytic activity of holocellulose hybrids.