Zn2+ induced hierarchical all bio-based supramolecular folate/alginate dual network leading to ultra-light and fire-safety aerogels

Aerogels based on supramolecular self-assembly have become one of the hotspots in aerogel research. Herein, we reported a full biobased hierarchical supramolecular aerogel with low density, excellent flame retardant and fire-warning response which was obtained via a simple supramolecular self-assembly of folic acid tetramer (FA-tetramer) and sodium alginate. The density of the resultant FSNZ aerogels was ultralow at 14.4∼17.8 mg/cm³, and the thermal conductivity reaches as low as 33.6 mW/(m∙K). Moreover, the resultant aerogel showed an excellent flame-retardancy and early fire warning capability (responses within 3 s), The heat and smoke release value were reduced by 53.6 % and 82.3 %, respectively. The flame-retardant mechanism of FSNZ aerogels is attributed to the zinc-catalyzed carbonization of FA-tetramer and alginate, while the fire early-warning mechanism is based on the temperature-responsive semiconducting properties resulting from the synergistic effect of zinc oxide and graphitic residue char. As a result, the supramolecular FSNZ aerogels in this work provide a novel strategy for the preparation of flame-retardant aerogels.