Enhanced photocatalytic degradation of sulfathiazole via dual-ligand Zr-MOFs: A porphyrin and pyrene-based energy transfer

Energy transfer (EnT) has been identified as an effective method to facilitate charge separation and improve photocatalytic performance. However, EnT has rarely been used in the photocatalytic degradation of pollutants. In this study, the arrangement of organic ligands in metal-organic frameworks (MOFs) was precisely engineered to enable efficient EnT among ligands. The compounds TCx-TB10 (X = 3, 4, 5, 6, 7, 8) were synthesized through solvothermal and technique, employing 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and 1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy) as ligands for the photocatalytic degradation of sulfathiazole (STZ). Among these, TC4-TB10 achieved the highest degradation efficiency, with a removal rate of 93.09 % for STZ. When similar photocatalytic tests were conducted on ranitidine (RAN), nizatidine (NZT), tetracycline (TC), and gatifloxacin (GAT), TC4-TB10 continued to demonstrate outstanding photocatalytic activity, showing removal efficiencies of 95.85 %, 95.30 %, 86.50 %, and 85.85 %, respectively. The effective EnT mechanism from TBAPy to TCPP in TC4-TB10 was confirmed through fluorescence and photocatalytic oxidation studies. Furthermore, singlet oxygen (1O2) was identified as the main reactive oxygen species involved. Proposed degradation pathways for STZ were outlined based on DFT calculations and UPLC-HRMS analysis. The Toxicity Estimation Software Tool (T.E.S.T.) was used to predict that STZ and its degradation products would largely exhibit low or no toxicity. Notably, 1O2 demonstrated remarkable resistance to interference, not being affected by most inorganic ions and humic acid (HA), which allowed TC4-TB10 to maintain high STZ removal rates even in real water samples. This research extends the potential applications and offers important insights into employing the EnT process for enhancing the photocatalytic capabilities of MOFs.