Ice-confined dual cross-linking enables robust biopolymer aerogels for oil–water separation and solar-driven water purification

Biopolymer-derived aerogels are gaining attention as sustainable and environmentally friendly substitutes for traditional synthetic counterparts. However, their large-scale utilization has been constrained by complicated preparation steps and limited mechanical integrity. In this work, we propose a low-cost and efficient route to construct robust chitosan/cellulose nanofiber (CS/CNF) aerogels through an ice-confined in situ dual cross-linking process that integrates physicochemical interactions, followed by rapid ambient-pressure drying. A subsequent dip-coating with polydimethylsiloxane (PDMS) and thermal curing further enhanced the surface and interfacial stability of the materials. The resulting CS/CNF@PDMS composite aerogels exhibit superior compressive strength (340 kPa at 80% strain), low thermal conductivity (42.7 mW m −1  K −1 ), and improved flame-retardance when subjected to direct butane flame for 20 s. Benefiting from the robust hydrophobic skeleton, the aerogels achieve efficient oil–water separation with high adsorption capacities (16.8–33.2 g/g) for various oils and organic solvents, maintaining excellent reusability. Additionally, the MXene-modified CS/CNF aerogel delivers a solar-driven water evaporation rate of 2.02 kg m −2  h −1 under one-sun illumination in simulated seawater with evaporation efficiency exceeding 96%. This straightforward and scalable strategy produces biopolymer-based aerogels that are mechanically durable, thermally insulating, flame-retardant, and multifunctional, offering broad potential for environmental cleanup and solar-assisted water purification.