Wood is a renewable and eco-friendly resource with great promise to advance sustainability in various industries, particularly those associated with construction and building materials. To maximize wood uses, here we show a processing route that transforms low-value wood (residual, damaged, decayed, disposed or fractured) into lightweight and strong structural materials. The process involves delignification, combined with partial dissolution and regeneration, to expose cellulose fibrils originally present in the cell walls. The latter form strong hydrogen bonding networks at interphases, leading to a ‘healed’ wood with a mechanical strength that exceeds that of typical metals and commercial laminated wood. Moreover, recyclability as well as excellent resistance against organic solvents are demonstrated, providing a promising valorization and sustainability pathway for low-value wood.
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We acknowledge funding support from the National Natural Science Foundation of China (32001256); China Postdoctoral Science Foundation (2020M681067 and 2021M700734); the Fundamental Research Funds for the Central Universities (2572020BB02); the Natural Science Foundation of Heilongjiang Province (YQ2021C004); the Canada Excellence Research Chair Program (CERC-2018-00006) and Canada Foundation for Innovation (project no. 38623).
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Extended Data Fig. 1 Raman spectra analysis of the cell walls of wood fibres from natural and delignified wood.
a, Optical microscope image of the natural wood. Inset: Raman mapping of the natural wood cell walls. b, Raman spectra at different regions of the natural wood including the cell wall (CW), middle lamella (ML), and cell corner of middle lamella (CCML). The characteristic bands of lignin occur at 1605 and 1667 cm−1. c, Optical microscope image of the delignified wood. Inset: Raman mapping of the delignified wood cell walls. d, Raman spectra of the delignified wood showing the disappearance of Raman characteristic bands of lignin in CW, ML and CCML, demonstrating the removal of lignin.
a, Cross-sectional SEM image of the natural wood showing the compact cell wall. b,c, and d, Cross-sectional SEM images of the delignified wood revealing densely packed cellulose nanofibers exposed in the cell wall, with numerous nanoscale pores.
a,b, Cross-section, c,d, radial-section, and e,f, tangential-section showing the fibrillated structures inside the cell lumens.
a,b, L-directional SEM images of the healed wood revealing the highly aligned cellulose fibrils. c, Magnified SEM image of the healed wood demonstrating the well distribution of regenerated cellulose on the wood cell walls.
a, Optical image of the cracked wood treated by LiCl/DMAc showing the dissolution of cellulose fibrils at the fracture. b, The interface of cracked wood filled by regenerated cellulose after water bath for 5 minutes. c,d, Magnified optical images of the interface of healed wood revealing that the regenerated cellulose fibrils aggregated at the cracked interface.
Extended Data Fig. 6 Stability of healed and repaired wood using commercial adhesives upon immersion in acetone.
a, Photograph of the healed wood and cracked wood bonded by various commercial adhesives. b, Photograph of different wood samples immersed in acetone for 0.5 h. c, Photograph of different wood samples immersed in acetone for 2 h showing the breakages at the repaired site when the given commercial adhesive was used. d, Photograph of wood samples immersed in acetone for 10 h exhibiting the intact structure of healed wood.
a, Photograph and b, SEM image of basswood. c,d, SEM images of the regenerated basswood showing crosslinked cellulose networks inside the lumina. e, Photograph and f, SEM image of the paulownia wood. g,h, SEM images of the regenerated paulownia wood showing crosslinked cellulose networks inside the wood lumina. i, Photograph and j, SEM image of cedar wood. k,l, SEM images of the regenerated cedar wood showing crosslinked cellulose networks inside the lumina. m, Photograph and n, SEM image of pine wood. o, p, SEM images of the regenerated pine wood showing crosslinked cellulose networks inside the lumina.
Extended Data Fig. 8 Mechanical properties and microstructural characterization of various wood samples.
SEM images of (a, d, g, j) cracked and (b, e, h, k) healed basswood, paulownia wood, cedar wood and pine wood, respectively. In all cases, the images show that cellulose regeneration leads to nanofibrils arranged at the fractured zone, in a chain-like interface structure. The corresponding mechanical properties are shown in (c, f, i, l) for the tensile stress–strain profiles of the natural and healed wood along the L-direction. For instance, 49 MPa and 154 MPa, respectively for basswood and likewise for paulownia wood (44.7 MPa and 152.3 MPa), cedar wood (28.1 MPa and 105.1 MPa) and pine wood (64.8 MPa and 86.6 MPa).
Extended Data Fig. 9 Mechanical properties of healed wood prepared from waste wood (residential disposed furniture).
Photographs of a, discarded waste furniture, b, separated painted wood strips and corresponding c, delignified, d, regenerated and, e, healed wood. f, Tensile stress–strain curve of the healed wood prepared from waste furniture along the L-direction showing excellent mechanical properties (tensile strength of ~80 MPa).
Photographs of a, discarded wood branches, b, splintered wood branches, and corresponding c, delignified, d, regenerated and, e, healed wood. f, Tensile stress–strain curve of the healed wood prepared from wood branches along the L-direction showing excellent mechanical properties (tensile strength of ~98 MPa).
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Dong, X., Gan, W., Shang, Y. et al. Low-value wood for sustainable high-performance structural materials. Nat Sustain (2022). https://doi.org/10.1038/s41893-022-00887-8