Deep Eutectic Solvents Ignition-Triggered Interfacial Fusion for Structural-Grade Lignocellulosic Boards

Lignocellulosic structural boards are often regarded as sustainable materials, yet most still depend on fossil-derived thermoset resins that generate volatile emissions, form weak and irreversible bonded interfaces, and complicate circular end-of-life management. Here, we introduce deep eutectic solvent (DES) ignition-triggered interfacial fusion, a closed-loop strategy that replaces external adhesives through a 2-stage sequence. In the ignition stage, a minimal amount of recyclable DES selectively activates lignocellulosic cell walls and mobilizes native lignin/hemicellulose toward particle contact zones, creating an interface-ready state. In the subsequent fusion stage, hot pressing reconstructs and locks these redistributed components into a continuous, lignin-rich bonding interphase, yielding an adhesive-free BioFuse-Board. The resulting BioFuse-Board delivers an internal bond strength up to 2.53 MPa (vs. the 0.45 MPa commercial requirement) and a 24-h thickness swelling of 10.05%. Mechanistically, ignition promotes β-O-4 bond cleavage, lowers lignin molecular weight, and enriches phenolic and carboxyl sites, whereas fusion promotes condensation while depleting reactive sites, consistent with a locked interfacial network involving oxygen-bridged environments, lignin-rich C-C connectivity, and strengthened hydrogen bonding with cellulose. Beyond performance, the same ignition-fusion architecture embeds circularity via reagent reuse, stream valorization into wood adhesives, and mechanical remanufacturing of end-of-life boards. Technoeconomic and cradle-to-gate life-cycle analyses further demonstrate that DES ignition-triggered interfacial fusion is economically viable and substantially reduces environmental impacts. Collectively, this strategy provides a generalizable route to circular manufacturing of structural-grade, adhesive-free lignocellulosic structural materials.