High-performance cellulose-based engineering materials derived from coconut shell

Cellulose-based materials are gaining attention as sustainable alternatives to petroleum derivatives due to their minimal environmental impact and carbon emission. However, inherent limitations of cellulose-based materials, such as soft, irregular shape and inflammable, have hindered their broader application in engineering fields. Herein, we presented an “extraction-strengthening-reassembly” strategy to develop renewable and high-performance cellulose/zirconia (Zr@CSU) composite bulk materials through in-suit growth ZrO₂ strengthening phase on the capsule-shaped cellulose units extracted from discarded coconut shell. The reassembled Zr@CSU bulks not only showed the similar microstructure of natural coconut shells, but also possessed enhanced mechanical properties due to the strengthening of microcrystal interfaces between building units. Zr@CSU bulks had flexural strength of 101.86 MPa, modulus of 14.15 GPa and fracture toughness of 1.48 MPa m^1/2. In addition, the zirconia reinforced components enable Zr@CSU with lower peak values of heat release rate (HRR) and total heat release (THR), showing superior flame resistance. Furthermore, scalable Zr@CSU bulks with various sizes could be easily assembled and showed good processability. This sustainable approach provides a pathway for reducing biomass residues and carbon emissions, and creating high-value engineering materials from renewable resources.