Multifunctional cellulose nanofibrils-based composite film with superior mechanical strength and flame retardancy

Flammability remains a major challenge for the widespread application of cellulose-based films. To overcome this limitation, we developed a high-performance composite film (CCTCo) with superior mechanical strength and flame retardancy. The film was based on cellulose nanofibrils (CNs), titanate nanofibers, carbon dots, and Co-based metal-organic frameworks (Co-MOFs), and was fabricated using a novel strategy, SPFN. The CCTCo achieved a tensile strength of 39.8 MPa and an elongation at break of 37.5 %, outperforming most cellulose-based nanocomposites. Furthermore, it demonstrated exceptional flame retardancy, with an 86.2 % reduction in peak heat release rate and a 44.1 % decrease in total heat release compared to the CNs film. Mechanistic studies confirmed the effectiveness of the proposed strategy, SPFN, which combines surface charge inversion, physical morphology modulation, functional nanoparticle incorporation, and network structure construction. This study presents a novel strategy to overcoming the flammability limitations of CNs-based films, unlocking their potential for next-generation multifunctional films, particularly for sustainable packaging applications.