One-Step Construction\nof Hierarchical Porous and Defect-Rich\nZn<sup>2+</sup>-Doped NH<sub>2</sub>‑MIL-125(Ti) to Enhance\nPhotocatalytic Degradation of Tetracycline Hydrochloride

The\ndevelopment of efficient metal–organic framework\n(MOF)\nphotocatalysts for the degradation of tetracycline hydrochloride (TC)\nis crucial for environmental and public health. Herein, NH<sub>2</sub>-MIL-125(Ti) flakes (namely, Zn<sub><i>x</i></sub>Ti<sub>1–<i>x</i></sub>-NML), featuring defect-rich and\nZn<sup>2+</sup>-doping, were synthesized using a one-step solvothermal\nmethod. For the first time, the crystal structure of Zn-doped NML\nwas determined by combining extended X-ray absorption with fine structure\nspectroscopy. The formation mechanisms of the flake morphology with\nhierarchical porous structures were thoroughly investigated. Compared\nto NH<sub>2</sub>-MIL-125(Ti), Zn<sub>0.15</sub>Ti<sub>0.85</sub>-NML\nachieved a 3.4-fold increase in removal of TC under simulated sunlight.\nThe adjusted electronic structure enhances superoxide radical production,\ncoupled with a flake-like and porous architecture that promotes reaction\nsites, improved mass transfer, and reduced charge distances. Combined\nwith theoretical calculations of the density of states and electrostatic\npotential, the ligand–metal–metal charge transfer process\nwas elucidated. The possible pathway for the photocatalytic degradation\nof TC by Zn<sub>0.15</sub>Ti<sub>0.85</sub>-NML was further speculated.\nMoreover, the safety of the photocatalytic pathway was assessed by\npredicting the toxicity of the degradation intermediates. Our findings\nlink the structure of MOFs to their catalytic efficiency, guiding\nthe creation of sustainable photocatalysts.