Highly Water-Stable and Visible-Light-Responsive Ag@Al-TCPP MOFs for Enhanced Photochemical Transformation of Tetracycline

In this study, a series of Ag@Al-TCPP metal-organic frameworks (MOFs) with uniformly dispersed, small-sized silver nanoparticles (Ag NPs) on starfruit-shaped porphyrin Al-MOFs were fabricated through a facile two-step process involving hydrothermal and solvent-assisted thermal reduction methods. Benefiting from the excellent light-harvesting ability of the porphyrin ligand, the strong coordination of Al-O bonds, and the modification of Ag NPs, Ag@Al-TCPP MOFs exhibit broad light absorption, good chemical stability, and enhanced photogenerated charge separation and transfer. Under visible-light irradiation, Ag@Al-TCPP-2 achieved a removal efficiency of 86.3% for 20 mg L-1 tetracycline (TC) in a 50 mL solution within 90 min, with the average photodegradation rate of TC being 0.169 mg L-1 min-1. This situation is approximately 1.32 times higher than that of pure Al-TCPP (0.128 mg L-1 min-1). Radical trapping experiments and electron paramagnetic resonance tests demonstrated that photogenerated holes and superoxide radicals (•O2-) are the key reactive species responsible for the degradation of TC. What's more, research indicates that the Ag NPs modification renders Al-MOFs thermodynamically more conducive to •O2- generation, leading to improved TC degradation performance. This study provides a convenient and effective approach for synthesizing highly efficient water-stable MOF-based photocatalysts for the treatment of antibiotic pollution.