Multiple Strategies Enhance the ROS of Metal–Organic Frameworks for Energy-Efficient Photocatalytic Water Purification and Sterilization

The development of novel photocatalytic systems for energy-saving and efficient water purification and sterilization is extremely challenging but crucial for the prevention of chronic diseases caused by water pollution and bacteria. The self-aggregation of photosensitizers (PSs) driven by tight π–π stacking leads to a sharp decline in the ability to generate reactive oxygen species (ROS) and has become the main bottleneck for the application of PSs in photocatalytic water purification and sterilization. Herein, a series of porous anthracene-based metal–organic frameworks (MOFs) {[Zn(L)2(DEF)2]n·2nDEF·nH2O (GXNU-1), [Co2(L)4(DEF)2]n·4nDEF·8nH2O (GXNU-2), and [Ni(L)2(DEF)2]n·nDEF·4nH2O (GXNU-3)} with excellent ROS generation ability were designed and synthesized. The energy level structures of GXNU-1–3 were determined by electrochemical experiments, which proved that all the frameworks have the ability to produce 1O2. In addition, the photocurrent response and electrochemical impedance spectroscopy (EIS) proved that the formation of MOF structures can effectively enhance the charge separation ability and promote photogenerated holes and excitons under light-driven conditions, thereby further promoting the rapid generation of ROS. Their ability to catalyze the rapid purification and sterilization of high-concentration dye wastewater under low-power (60 mW·cm–2) light irradiation was then determined. The porous framework structure prevents the tight π–π stacking of anthracene-based PSs and increases the contact sites with oxygen. Moreover, the introduction of metal ions promotes the intersystem crossing of excitons through spin–orbit coupling. These advantages greatly enhance the ROS generation ability of GXNU-1–3 in aqueous solutions. Notably, GXNU-1–3 almost completely degraded high-concentration organic dyes, such as crystal violet (CV), methylene blue (MB), rhodamine B (RhB), and orange II (OII). In addition, GXNU-1 efficiently degraded mixed organic dyes of CV (30 mg·L–1) and MB (10 mg·L–1) within 30 min of light irradiation, thereby showing a surprising ability to purify multicomponent dye wastewater. The heterogeneous GXNU-1–3 can be rapidly separated from the aqueous solution by centrifugation and filtration to avoid secondary pollution. More notably, GXNU-1 can effectively inhibit the rapid proliferation of Gram-negative/positive bacteria under light irradiation conditions. Masks and experimental clothes soaked in a GXNU-1 aqueous solution for 15 s clearly resisted bacterial contamination after being exposed to 60 mW·cm–2 light irradiation for 4 min. These findings open new horizons for the construction of novel photocatalytic systems that are fast, efficient, and environmentally friendly.