Metal-polyphenol networks facilitate the construction of recyclable fiberboard

The global annual fiberboard production is approximately 53 million tons, yet its current recycling rate is less than 20%. The fundamental cause lies in the synthetic adhesives used in production, such as urea-formaldehyde and phenolic resins, which form chemical bonds that are difficult to cleave during bonding, hindering the recycling and reuse of fiberboard. Therefore, a dynamically reversible bonding strategy is desirable to facilitate fiberboard recycling while maintaining adequate strength and environmental safety. Metal–polyphenol networks (MPNs) exhibit several advantages, including rapid bonding, moderate binding energy, environmentally friendly synthesis, and reversible responsiveness. This study demonstrates that coordination interactions between metal ions and polyphenolic compounds form a dynamic supramolecular network, whereby board bonding is achieved through in situ self-assembly of MPNs within the fiber network, enabling the fabrication of recyclable fiberboards with integrated bonding functionality without the addition of conventional synthetic adhesives. The internal bonding strength of the resulting recyclable fiberboard reaches 2.6 MPa, static bending strength is 46 MPa, and 24-hour thickness swelling upon water absorption is 11%, showing mechanical performance comparable to or exceeding that of most biomass adhesives. After four cycles of reuse, the bonding strength retains 76%. The formaldehyde release of recyclable fiberboard is far below the ENF (European Norm for Formaldehyde) standard, and concentrations of total volatile organic compounds (TVOCs), benzene, toluene, and xylene are all below the detection limit, demonstrating both recyclability and carbon reduction potential, thus contributing to a circular economy.