Design of Multilayer Cellulose-Based Filters Combined with Zeolitic Imidazole Framework and Silica Nanoparticles for Particulate Matter Filtration and Antibacterial Properties

Owing to growing concerns of air pollution and environmental issues, cellulose-based air filters have recently been introduced as an alternative to fossil fuel-based polymers in air purification systems. However, producing high-purity cellulose with optimal properties suitable for air filter fabrication remains the main challenge for this application. Herein, we optimized the production method of cellulose from pulp biomass via acid hydrolysis in combination with mechanical treatment with a high-speed homogenizer (HS) or ultrasonication (US). After that, the various synthesis conditions of zeolitic imidazolate frameworks-8 (ZIF-8) were performed. For the filter fabrication, ZIF-8 and NS/CDs@MSN were then introduced into a nanocellulose matrix, and subsequent TBA-induced freeze-drying was applied to create antibacterial multilayer cellulose-based filters. The results revealed that highly pure cellulose, size, and morphology of nanocellulose were optimized under 6 h of acid hydrolysis with 1.5 h of HS. The deposition of ZIF-8 and NS/CDs@MSN into the nanocellulose matrix was found to increase the porosity of the cellulose-based filter and provide a stable network structure. For the particle filtration efficiency (PFE) test with 0.5, 1.0, and 1.5 μm particle sizes, the filter showed an excellent PFE of 86.44% for 1.5 μm particles with a quality factor of almost 0.01 Pa^–1. Moreover, the material exhibited sufficient antibacterial activity against airborne bacterial growth, especially Staphylococcus aureus. It is proposed that the reactive oxygen species generated by NS/CDs@MSN and Zn²⁺ from ZIF-8 play an important role in inactivating bacteria. Overall, this work demonstrates the idea of a multifunctional air filter with excellent performance in both air purification and bacterial control, paving the way toward sustainable air filtration.