Antibacterial and flame-retardant TEMPO-oxidized cellulose nanofibrils/chitosan-based sponge for efficient PM2.5 capture

PM2.5, which can carry many bacteria, poses a serious threat to health when inhaled. Therefore, developing porous materials with efficient filtration and antibacterial properties is essential for preventing the invasion of PM2.5 on respiratory health. In this study, we designed a multifunctional sponge filter through the synergistic integration of TEMPO-oxidized cellulose nanofibrils (TCNF), chitosan (CS), graphene oxide (GO), and lignin hybrid particles. A robust three-dimensional network was constructed via amide cross-linking between TCNF and CS, endowing the sponge with exceptional mechanical stability. GO enhances the PM2.5 interception efficiency through electrostatic adsorption. Additionally, we introduce lignin nanoparticles (LNP) as carriers for growing zinc oxide (ZnO), forming organic-inorganic hybrid particles (LNP@ZnO). This approach minimizes the negative impact of ZnO on the mechanical properties of the sponge while enhancing antibacterial performance. The resulting sponge filter demonstrates high PM2.5 filtration efficiency (99.14 %) with low pressure drop (38 Pa), excellent antibacterial properties against E. coli (92.63 %) and S. aureus (89.05 %), and outstanding flame-retardant properties (LOI value of 27.1 %). This study addresses the limitations of existing systems by minimizing the trade-off between antibacterial performance and mechanical strength, offering a novel approach for the design of advanced air filtration materials.