Ce(III)-Doped Mixed-Valence Metal-Organic Frameworks Boosting Ligand-To-Metal Charge Transfer for Photooxidation of a...

Due to the high toxicity and potential threats to society, extensive efforts are devoted to developing catalysts for efficient photodegradation of mustard gas. Metal-organic frameworks (MOFs) are considered as promising candidates for photooxidation, but the limited charge separation efficiency of the pristine MOFs restricts their further applications. Herein, through a one-pot synthesis strategy, Ce(III) ions are incorporated in a Ti-based porphyrin MOF (DGIST-1), leading to a mixed-valence MOF with enhanced charge transfer efficiency. Thanks to the unique electronic structure of Ce(III) and redox ability of porphyrin ligands, the Ce(III)-doped MOF exhibits remarkable photodegradation ability toward the sulfur mustard-gas simulant with a short half-life (t_1/2 = 1.60 min) and, more importantly, a high turnover frequency (TOF = 2.08 s^-1), which is significantly outperformed the reported photocatalysts, even most of the noble metal-based photocatalysts. Mechanistic studies and theoretical calculations demonstrate that the introduction of Ce(III) can notably improve the charge transfer efficiency via ligand-to-metal charge transfer, thereby promoting the activation of O₂ to reactive oxygen species and the degradation of mustard-gas simulant.