Scalable fabrication of sustainable, recyclable and multifunctional graphene−cellulose foam for efficient photothermal water evaporation

Lightweight and robust foams with multifunctionality are highly desirable to meet the demands of resource conservation and the development of an environmentally friendly society. Here, we demonstrate a sustainable and recyclable composite foam made from abundant resources of kapok cellulose and graphene as raw materials, produced through ionic (Cu 2+ ) crosslinking and directional freezing techniques. The resulting composite foam exhibits a low density of 18.6 mg cm −3 , a high compression modulus of 12.5 MPa, and exceptional thermal insulation performance of 0.02 W m −1  K −1 . An interpenetrating network formed through the chelating effect of Cu 2+ and physical crosslinking within the foam provides excellent wet stability and flame self-extinguishing ability, all while ensuring remarkable recyclability (the Young's modulus retains 96 % of its original foam after five recycling cycles). Additionally, the ice templating enhances the alignment of graphene nanoplatelets, resulting in pronounced anisotropic properties in mechanical strength, thermal conductivity, and electromagnetic shielding. This unique pore structure boosts its potential for use in photothermal water evaporation devices, achieving a water evaporation rate of 1.91 kg·m −2  h −1 and an evaporation efficiency of 80.5 % under 1.0 sun irradiation. This innovative method represents a significant breakthrough in the development of sustainable, high-performance foams, thus broadening their potential applications.