Defence of doctoral thesis: Xiaoying Xu – Wood Nanoengineering for Multifunctionality through Metallization and Mineralization

Hierarchical porous materials yield versatile functionalities by combining pores across multiple length scales, whereas their controlled bottom-up synthesis remains a challenge. This thesis presents a biomimetic strategy to fabricate hierarchical porous metal and mineral composites by utilizing and exploring the naturally developed hierarchical structure of wood. Direct use of wood as template is also environmentally and economically friendly due to its renewable source, low cost, and scalable processability. 

A sequential methodology was developed, beginning with cell wall engineering to overcome the limited accessibility and mass diffusion of bulk wood. This was first achieved by programmed removal of cell wall components. Reassembly of intrinsic biopolymers into lumina fibril networks was then investigated to create wood aerogels with high specific surface area. The engineered wood scaffolds were subsequently functionalized via metallization or mineralization. Electroless Cu plating produced compressible, electrically conductive templates, while MTMS condensation imparted hydrophobicity. ZnCl2 was also explored to simultaneously fabricate wood aerogels and precipitate ZnO in situ. The resulting composites combined the structural advantages of engineered wood scaffold (large surface area, aligned channels, mechanical robustness) with the functionality of guest materials. This synergy enables applications in pressure sensors, thermal insulation in energy-efficient buildings, and photocatalytic dye degradation. This work established a versatile and sustainable platform for transforming renewable resources into high-performance functional composites. 

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