Biomimetic Nanostructured Polyimine Aerogels with Graded Porosity, Flame Resistance, Intrinsic Superhydrophobicity, and Closed-Loop Recovery

Polymer aerogels, with their porous and lightweight features, excel in applications such as energy storage, absorption, and thermal insulation, making them a sought-after new material. However, the covalent cross-linking networks of current polymer aerogels result in unsustainable manufacturing and processing practices, persistently depleting our finite natural resources and causing significant global environmental impacts. Herein, we have constructed a high-performance dynamic covalent cross-linking aerogel network using biobased materials, with its structure and green sustainability akin to those of plants in nature. Abundant reversible cross-linking points endow the aerogel with ultrafast degradation capabilities, enabling allow for closed-loop chemical monomer recovery and reprocessing. Furthermore, utilizing the highly active reversible network, net-zero emission material reuse and reprocessing can be achieved. Additionally, the controlled dynamic aerogel network features a multilevel roughness nanostructured surface similar to lotus leaf and a biomimetic pore structure, contributing to significant anisotropy. The distinctive structure and composition endow the dynamic aerogel with high compressive strength (2.2 MPa) vertically, low thermal conductivity (0.0257 W/(m·K)) horizontally, and outstanding fire resistance (LOI is as high as 36%). Notably, the aerogel demonstrates the highest hydrophobicity among polyimine materials, with a contact angle of 154°. Furthermore, those dynamic aerogels have excellent performance in a variety of potential applications such as oil–water separation, directional transport, and phase change energy storage, and it is anticipated that these applications will greatly benefit from systematic upgrades in recyclability and reprocessing.