Dual-mode (light/dark) active nanocellulose–MOF–carbon dot filters for airborne bacterial suppression in hospital environments

Airborne microbial contamination in hospitals is a major driver of healthcare-associated infections (HAIs). So far, most commercial air filters capture microorganisms but do not inactivate them, and they rely on non-biodegradable polymers. Here, we engineered bio-derived nanocellulose filters from oil palm empty fruit bunches and endowed them with dual-mode (light/dark) antimicrobial activity by integrating zeolitic imidazolate framework-8 (ZIF-8) and N/S-doped carbon dots immobilized on mesoporous silica nanoparticles (NS/CDs@MSN). Three-dimensional, highly porous scaffolds were fabricated via tert-butyl alcohol-assisted freeze-drying, yielding interconnected channels that promote airflow and contact between airborne bacteria and the active surface. Hospital air was sampled using a six-stage cascade impactor equipped with a cellulose filter, after that culture-based assays and MALDI-TOF/MS were used to characterize the trapped microorganisms. While pristine nanocellulose filters allowed survival of opportunistic pathogens, including Bacillus cereus, Bacillus thuringiensis and Staphylococcus epidermidis , the ZIF-8+NS-CDs@MSN composite filters achieved wide-ranging suppression of culturable airborne bacteria captured on the filter surface and within the filter matrix. Electron spin resonance (ESR) spectroscopy confirmed the generation of multiple reactive oxygen species (ROS), including •OH, 1 O₂, and •O₂⁻, under both dark and 365 nm irradiation, supporting a dual-mode, ROS-driven inactivation mechanism that is synergistic with the presence of Zn-containing phases. Characterization via Nano-CT and XRF confirmed the uniform distribution of ZIF-8 and MSN within the 3D nanocellulose matrix, which optimized particulate capture and radical-pathogen contact. This study demonstrated a sustainable, ROS-active nanocellulose–MOF–carbon dot platform that bridges real-world hospital air monitoring and on-filter disinfection, offering a promising route to next-generation antimicrobial air-filtration materials for infection control in healthcare environments.