Porphyrinic based hydrogen-bonded organic framework/TiO2 nanocomposites for efficient photocatalytic degradation of sulfadiazine

Porphyrinic hydrogen-bonded organic frameworks (porph-HOFs) have emerged as highly promising materials in the realm of photocatalysis due to their remarkable attributes, including low density, high surface area, efficient visible light absorption, and notable chemical stability. However, the rapid recombination of photogenerated charges remains a significant concern. In this work, a novel HOF-based photocatalyst, PFC-72/TiO2 was successfully designed with visible light response and high electron transfer capability. This involved bonding TiO2 nanoparticles to the PFC-72 framework synthesized using cobalt porphyrin as organic ligand and introducing bridging molecules 4-mercaptopyridine (4-PySH). Moreover, sulfadiazine (SDZ), a highly prevalent antibiotic, was effectively degraded from wastewater using PFC-72/TiO2. The high specific surface area of PFC-72 significantly improved the dispersion of TiO2 in PFC-72/TiO2, providing more active sites and improving the ability to adsorb SDZ. Characterizations and density functional theory analysis further confirmed that the photosensitization effect of porph-HOF extended the response range of TiO2 in PFC-72/TiO2 and reduced the recombination efficiency of photogenerated charges, consequently enhancing photocatalytic performance. Additionally, due to significantly improved robustness of PFC-72 and its axial coordination interaction with 4-PySH, PFC-72/TiO2 displayed excellent stability and recyclability. Consequently, optimized PFC-72/TiO2 exhibited a remarkable SDZ removal efficiency of 93.7 % within 120 min, maintaining consistent photoactivity even after undergoing four cycles. Furthermore, intermediate products and degradation pathways were proposed based on UPLC-MS/MS.