Rapid microwave synthesis of PCN-134-2D for singlet oxygen based-oxidative degradation of ranitidine under visible light: Mechanism and toxicity assessment

Two-dimensional porphyrin metal-organic frameworks (2D-PMOFs) showed potential applications in the field of photocatalysis. In this study, PCN-134-2D was rapidly prepared by the microwave-assisted solvothermal (MS) method for photocatalytic degradation of ranitidine (RAN), and exhibited enhanced photocatalytic performance due to the augmentation of the TCPP/BTB ratio (0.55). 93.1% of RAN could be effectively photodegraded in 120 min through PCN-134-2D under visible light. During the photosensitizing process, singlet oxygen (O-1(2)) was proved to be the major reactive oxygen species (ROS) and showed the unique ability of non-radical resistance to conquer the inhibiting effects of inorganic anions (Cl-, HCO3, NO3, SO42-, H2PO4) and natural organic matter (humic acid [HA]). The effects of practical reaction parameters were studied in detail. Light intensity and oxygen content were demonstrated as the key factors to photosensitization. The final removal rates of RAN in lake waters and river waters were 84.7% and 84.1% under the solar light. Meanwhile, the total organic carbon (TOC) removal rates were 30.4% and 31.5%, respectively. Ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to analyze the photodegradation products of the target RAN, and 17 intermediate compounds were obtained in ESI positive mode. The degradation pathways of RAN by O-1(2) were proposed as C-N bond and C-S bond cleavage. Ecotoxicity assessment by the Ecological Structure Activity Relationships (ECOSAR) program indicated that most of the intermediate products were "not harmful" to fish, daphnid and green algae. The inhibition rate of Vibrio fischeri bioluminescence was approximately reduced 62% after RAN was treated by PCN-134-2D in 120 min.