Amide-Based Porous Organic Polymers for Efficient Loading of Photosensitizers and Production of Reactive Oxygen Species for Antimicrobial Applications

The aggregation-caused quenching (ACQ) effect of photosensitizers (PSs) damages its photosterilization efficiency. Herein, two amide-bond connected porous organic polymers (POPs) containing a benzophenone structure (POP-1) and no benzophenone structure (POP-2) were designed and obtained. The high specific surface area (197.3 m2/g) and pore size (4.260 nm) of POP-1 enabled Rose Bengal (RB) to be efficiently trapped in POP-1 (RB@POP-1). Similarly, POP-2 showed a specific surface area of 28.63 m2/g and a pore size of 3.409 nm, which also ensured the capture of RB. Adsorption of RB by POP-1 decreased with increasing pH; and the equilibrium adsorption capacity (qe) of POP-1 for RB reached about 27.88 mg/g (the initial concentration of RB solution was 350.0 mg/L). The adsorption conformed to the Freundlich adsorption isotherm model and the pseudo-first-order kinetic adsorption model. The amount of reactive oxygen species (ROS) produced by RB@POP-1 and RB@POP-2 increased by 24.25% and 332.0%, respectively, compared with that produced by only POP-1 and POP-2, which mainly benefited from three aspects: (I) the separation distribution of RB molecules in the mesopores of POP-1 or POP-2 significantly decreased the ACQ effect; (II) the benzophenone structure and RB molecule of RB@POP-1 synergistically produced ROS under the light irradiation, resulting in a better antimicrobial effect of RB@POP-1 compared to the POP-1 and RB@POP-2; (III) besides the singlet oxygen (1O2), the hydroxyl radical (HO•) was also effectively produced because RB was surrounded by sufficient good hydrogen donors (H-donors) on POP-1 or POP-2, which was beneficial for RB to undergo the type I photoreaction. Due to the sufficient ROS, 99.99% of E. coli and S.aureus could be killed just within 10 min of exposure to light. This provides a feasible and effective approach for producing biocidal materials, such as the personal protective equipment or water purification.