Anchoring of silver nanoparticles by a zinc-porphyrin covalent organic framework for synergistic photodynamic sterilization

Porphyrin-based covalent organic frameworks (Por-COFs) show great promise in photodynamic sterilization and elimination of pathogenic bacteria. In this work, a two-dimensional Por-COF was constructed using 5,10,15,20-Tetrakis-(4-aminophenyl)-porphine-Zn(II) (Zn-TAPP) and Dihydroxyterephthalaldehyde (Dha), which was post-synthetically modified with silver nanoparticles (Ag NPs). Ag@ZnPor-COF delivered extraordinary photodynamic inactivation performance against Staphylococcus aureus and Escherichia coli under visible light (99.96 % and 99.75 %, respectively, within 20 min). The localized surface plasmon resonance of the Ag NPs enhanced the absorption of visible light whilst also aiding electron-hole separation, leading to efficient generation of reactive oxygen species (ROS), especially singlet oxygen (1O2). Further, the Ag NPs imparted Ag@ZnPor-COF with photothermal properties, thereby delivering even more effective control of pathogenic bacteria. Density functional theory (DFT) calculations validated the experimental findings, identifying Ag@ZnPor-COF as a potent antibacterial platform. Results encourage the wider use of Por-COFs and plasmonic nanomaterials in the development of antibacterial systems.