Tick-inspired, self-healing, and strongly-adhesive coatings with biodegradability and phosphorus-free fire retardancy

• A high-performance, fire-retardant coating (DCNC/40PEN) is developed; • DCNC/40PEN can adhere to different substrates and self-heal at room temperature; • DCNC/40PEN features closed-loop recyclability and biodegradation; • Phosphorus-free DCNC/40PEN provides superior fire protection for various materials. Although widely applied in diverse industries, conventional fire-retardant coatings generally suffer from poor adhesion and fire protection. These coatings are typically phosphorus-containing and non-recyclable, making their waste prone to causing environmental issues, e.g., bioaccumulation and (micro)plastic pollution. Inspired by the multi-non-covalent adhesion mechanism of ticks, we designed a strongly adhesive and self-healing coating (DCNC/40PEN) with superior fire protection by incorporating hydrogen bonding, π-π stacking, and cation-π interactions. Incorporating these interactions into a dynamic covalent network further imparts closed-loop recyclability and biodegradability to the coating. DCNC/40PEN can adhere to diverse substrates and self-heal at room temperature due to the non-covalent and covalent interactions within its structure. DCNC/40PEN features closed-loop recyclability and biodegradation because of its dynamic covalent network. Owing to the catalytic and crosslinking carbonization of sulfonate and Schiff base groups, phosphorus-free DCNC/40PEN delivers exceptional fire protection for various materials, e.g., wood, polymer foams, and steel. At a coating thickness of 100 μm, DCNC/40PEN significantly increased the limiting oxygen index and vertical combustion (UL-94) rating of wood to 35.0% and V-0. The multifunctionality and sustainability of DCNC/40PEN enable it to outperform commercial and reported fire-retardant coatings and adhesives. This work presents an innovative design strategy for the next generation of sustainable, versatile fire-retardant coatings, accelerating “green” development.