Multifunctional Chitosan Aerogels with Superior Mechanical Properties via Freeze-Confined Cross-Linking and Ambient Drying

Biomass aerogels, as low-density, high-porosity, and renewable materials, have attracted significant attention in recent years. Compared with vacuum drying and supercritical drying, ambient drying has potential for the large-scale production of aerogels but still faces challenges such as structural collapse. In this work, chitosan, a widely available polysaccharide, was employed to construct a lightweight, high-strength aerogel using an improved freeze-drying method. This strategy involves prefreezing to control the high-density cross-linking of chitosan, thereby reinforcing the wet gel skeleton and mitigating capillary-induced destructive collapse during subsequent ambient drying. The resulting aerogel features a robust porous architecture, delivering an exceptional mechanical strength of 0.76 MPa, outstanding compressive fatigue resistance, and low thermal conductivity of 46 mW/m·K at reduced density. In addition, the good hydrophobic properties of this aerogel were endowed by chemical vapor deposition and interfacial modification. Impressively, the obtained aerogel was further demonstrated to possess significant advantages in multifunctional applications such as impact resistance, thermal insulation, infrared stealth, and efficient oily wastewater treatment. We believe that the proposed improved freeze-drying method provides a simple yet effective approach for preparing high-performance biomass aerogels suitable for various practical applications.