Fabrication of multifunctional sodium alginate aerogel enhanced by in situ dual crosslinking with PVA and Zn2 + /Al3+

In order to address the urgent demand for sustainable thermal insulation materials, a biomass-based sodium alginate (SA) aerogel was developed through in situ dual crosslinking with polyvinyl alcohol (PVA) and Zn 2+ /Al 3+ in this work. The SAP-Al 0.15 aerogel demonstrated exceptional multifunctionality with ultra-low density (2.37 ×10 −2 g·cm −3 ), excellent mechanical strength (366.2 kPa longitudinal, 846.7 kPa transverse), and superior flame retardancy (LOI=30.4 % and UL-94 V-0 rating). Hierarchical pore architecture enabled remarkable thermal insulation (ΔT = 55 ℃ at 80 ℃ heating) and weight-bearing capacity (over 3300 times of self-weight). Systematic characterization revealed that Al³ ⁺ crosslinking preferentially enhanced network densification through strong carboxyl coordination, achieving 35.4 % char residue with protective Al 2 O 3 layers. Compared to SAP-Zn 0.15 , Al 3+ crosslinking increased compressive modulus by 377 % while maintaining 97.6 % porosity. This EDTA-mediated in situ dual crosslinking strategy successfully resolved the mechanical-thermal-flame retardancy comprehen-sive improvement in biomass aerogels, positioning SAP-Al 0.15 as an eco-friendly alternative to conventional insulation foams for architectural heat insulation. This work provided fundamental insights into the structure-property relationships of biopolymer-based aerogels, offering a sustainable materials platform for energy-efficient building applications.