Engineering the spatial distribution of metal-organic frameworks in lamellar wood sponges for superior thermal insulation and fire retardancy

The development of cellulose-based thermal insulation materials with integrated low thermal conductivity, high flame retardancy, and mechanical robustness is challenging for high-performance thermal management. Herein, a straightforward top-down strategy is proposed to develop a lightweight, anisotropic composite with integrated thermal insulation and fire retardancy by incorporating metal-organic frameworks (MOFs) into a carboxylated wood sponge (CWS). The resulting MOF@CWS composite exhibits an arch-shaped lamellar architecture with MOFs wrapping the lamellas, endowing it with temperature-tolerant compressive elasticity from − 196 °C to 200 °C. Leveraging the synergistic effects of the heat transfer anisotropy in the lamellar CWS and the decreased solid heat conduction induced by the discretely anchored MOFs, the MOF@CWS composite demonstrates superior anisotropic thermal insulation with a low thermal conductivity of 29.29 mW m − 1 K − 1 perpendicular to the lamella direction, outperforming most previously reported wood-based thermal insulators. Moreover, the fire retardancy of the composite depends on the specific MOFs incorporated. In particular, the thermally stable MIL-53(Al) nanolayers can effectively protect the cellulose scaffold from combustion with suppressed gas release, achieving a reduced peak heat release rate from 138 W g − 1 to 39 W g − 1 . With its compelling thermal insulation, fire retardancy, mechanical resilience, and fabrication scalability, the lamellar MOF@CWS represents a sustainable and promising alternative to conventional fossil-based insulators for advanced thermal management applications.