Bioinspired Enzymatic Mineralization Incorporates CaCO3 Mesocrystals in Wood for Surface Reinforcement and Flame-Retardancy

The development of sustainable strategies for the integration of wood with excellent mechanical and fire-retardant properties is increasingly appealing to bridge this renewable engineering material with multiple emerging applications. Inspired by biomineralization on soft tissues for a protective function, we developed enzymatic mineralization for the deposition of CaCO3 minerals in wood compartments. The immobilized urease in vessels and fibers increased the local concentration of bicarbonate anions, which, together with the directional diffusion of calcium cations, caused the deposition of calcitic CaCO3 mineral preferentially in cellular compartments of cells near the wood surface. The employment of the polymeric additives ensured that multistage mineralization started on the lumen-facing cell wall surfaces, and the local space in the lumina was filled with mesocrystalline CaCO3 deposits after multiple rounds of enzymatic mineralization. The incorporation of rod-shaped CaCO3 mesocrystals resulted in mineralized wood with improved surface hardness, and flame-retardancy, while at the same time, the moderate incorporation level preserved the intrinsic lightweight merit of wood. This bioinspired enzymatic mineralization approach can regulate the positioning and structure of functional minerals for the fabrication of high-performance mineralized wood in a sustainable manner.