Modulating Ligand-to-Metal Charge Transfer in Titanium-Oxo Clusters Enables Efficient H2O2 Activation and Pollutant Degradation

Abstract

Titanium-oxo clusters (TOCs), featuring atomically precise structures and tunable electronic properties, provide an ideal model for elucidating structure-activity relationships in heterogeneous Fenton-like catalysis. In this work, a series of titanium‑oxo clusters stabilized by various carboxylate ligands were employed to elucidate the relevant Fenton-like catalytic reactivity, where the superiority of Ti₄₄ cluster coordinated with propionic acid (Ti‑PA) for oxidative degradation was identified. We demonstrate Ti-PA-based hydrogen peroxide (H₂O₂) activation enables effective •O₂⁻ generation responsible for model substrate degradation. Crucially, ligand-to-metal charge transfer (LMCT) effects could dictate the relevant catalytic performance: small aliphatic carboxylate ligands (e.g., propionic acid) enabling appropriate LMCT effects facilitate H₂O₂ dissociation and promote •O₂⁻ release, while aromatic ligands suppress the activity by stabilizing key intermediates and impeding •O₂⁻ generation. Systematic spectroscopic analyses corroborate enhanced electron transfer and weakened intermediate binding in Ti-PA-H₂O₂ system. Theoretical calculations confirm the electron-deficient feature of Ti sites in Ti‑PA and the low energy barrier throughout the entire reaction pathway. This work highlights ligand engineering as a decisive strategy of rationally designing advanced titanium-based (Ti-based) Fenton-like catalysts.