Phase-change, biopolymeric cryogel-in-cryogel architecture for advanced heat management

Developing sustainable, multifunctional materials for dynamic thermal management is crucial for addressing the energy challenges. In this study, a novel dual-functional cryogel composed of birch bark-derived suberin and amphiphilic cellulose nanofibers (CNF) is fabricated in mixed and unique core–shell (cryogel-in-cryogel) configurations for advanced heat management with synergistic thermal insulation and thermal energy-storage capabilities. The CNF network serves as a mechanically robust, porous insulation scaffold, whereas suberin functions as a natural phase-change material providing latent heat-storage capacity. The resulting cryogels exhibit ultralow thermal conductivity (0.0324–0.0363 W/m·K), excellent compressive strength, and high structural integrity at high temperatures (∼170 °C). The unique cryogel-in-cryogel architecture efficiently prevents suberin leakage during phase transitions, offering superior shape stability and cyclic durability. Differential scanning calorimetry confirms the preserved latent heat-storage capacity of enveloped suberin. Importantly, the thermal effusivity increases with suberin content, indicating enhanced surface thermal interaction. Solar simulation tests demonstrate strong thermal insulation and buffering performance. This bio-derived architecture enables simultaneous thermal insulation and dynamic temperature regulation in a scalable, sustainable material platform. The findings offer advancements toward the development of high-performance, eco-friendly dynamic porous designs for buildings, electronic systems, and solar thermal storage. • Sustainable cryogels engineered from birch-bark suberin and cellulose nanofibers • Cryogel-in-cryogel architecture enables dual thermal insulation and energy storage • Cryogels exhibit ultralow thermal conductivity, excellent leakage resistance, and mechanical robustness • Increased thermal effusivity enables efficient heat absorption and release at the surface • Effective solar thermal buffering and structural integrity under thermal cycling