Halogen Substituents Regulate the Types of Reactive Oxygen Species Generated by Ca(II)-Based Luminescent HOFs, and Their Smart Sensing and Photodynamic Sterilization

Hydrogen-bonded organic frameworks (HOFs) have demonstrated unique application advantages in fields such as ion sensing and photodynamic sterilization. Herein, four HOFs were obtained by using 8-hydroxyquinoline with different heavy atom substituents to react with Ca(NO3)2·4H2O. Ca-HOFs all have excellent smart sensing performance behavior to SO42- ions, and their detection limits are 3.45, 2.15, 2.29, and 1.34 μM, respectively. In addition, Ca-HOF-1/3/4 also exhibits highly sensitive sensing performance behavior to Cr2O72- ions, and their detection limits are 0.833, 1.72, and 1.11 μM, respectively. Notably, light-driven switching of reactive oxygen species (ROS) in Ca-HOFs can be easily achieved by regulating the heavy atom substituents on the ligands. Ca-HOF-1 and Ca-HOF-2 containing -Cl substitution only efficiently produce type II ROS-1O2 under light irradiation conditions, while Ca-HOF-3 and Ca-HOF-4 containing -Br or -I substitution only produce type I ROS-•OH under light irradiation conditions. To the best of our knowledge, this is the first time that the generation of different types of ROS in HOF photosensitizers under light irradiation conditions has been regulated by changing the halogen-heavy atom substituents. This work not only opens a door for regulating the generation of specific ROS by photosensitizers but also promotes the development of efficient HOF-based photosensitizers.