Spider Silk-Inspired NIPU Adhesives with High Bonding Strength and Avoidance of Isocyanate Harm Derived from CO2 and Biomass

Following the implementation of stricter environmental policies, nonisocyanate polyurethane (NIPU) adhesives are shifting toward renewable biomass and CO2 utilization. However, their inferior mechanical properties compared to traditional PU hinder widespread application. Inspired by the microphase-separated structure of spider silk, this study introduces lignin as a β-sheet nanocrystal biomimetic into a linear CO2-based NIPU matrix. The resultant NIPU composite forms a three-dimensional hydrogen-bonding network formed between the hydroxyl groups of lignin and the NIPU matrix, achieving an enhanced tensile strength (15.07 MPa) and optimal bonding strength (1.52 MPa). This bioinspired strategy provides a novel route for valorizing lignin and CO2 while establishing foundations for high-performance NIPU adhesives.