Chitosan cryogels incorporated with phytic acid-modified UiO-66-NH2 for enhanced flame-retardant performance.

In this work, chitosan (CS) was used as the skeleton to synthesize flame-retardant composite cryogels. Phytic acid (PA)-modified Zr-based metal-organic framework (PA-UiO-66-NH2) was integrated into the CS network to enhance flame retardant performance. The vertical combustion test (UL-94) grade was V-0, and the limiting oxygen index (LOI) value reached 39 % when the flame retardant (PA-UiO-66-NH2) addition content was 15 %. Cone calorimetry tests demonstrated that the inclusion of PA-UiO-66-NH2 significantly decreased the heat release and smoke generation, facilitating the formation of a compact carbon layer on the cryogels. With a thermal conductivity of 0.03447 W/(m·K), the modified CS-15PA-UiO-66-NH2 cryogels maintained their superior thermal insulating capabilities as compared to the pristine cryogels. The water contact angle of the cryogels hydrophobically modified with methyl trichlorosilane (MTCS) was 135.3° ± 2.3°. This study presents cryogels with excellent flame retardancy, and such material is expected to replace conventional petroleum products in energy storage and building insulation.