Defect Engineering‐Driven Electron Spin Polarization and Charge Transfer in MOFs for Enhanced Sonocatalytic Therapy

Abstract Sonocatalytic therapy (SCT) is a non‐invasive tumor treatment modality that utilizes ultrasound (US)‐ activated sonocatalysts to generate reactive oxygen species (ROS), whose production critically dependent on the electronic structural properties of the catalytic sites. However, the spin state, which is a pivotal descriptor of electronic properties, remains underappreciated in SCT. Herein, a Ti‐doped zirconium‐based MOF (Ti‐UiO‐66, denoted as UTN) with ligand‐deficient defects is constructed for SCT, revealing the important role of the electronic spin state in modulating intrinsic catalytic activity. The defect‐driven sonocatalytic mechanism is elucidated as follows: 1) structural defects alleviate the limitations of ligand‐metal charge transfer, achieving a 2.1‐fold enhancement in charge transfer efficiency; 2) spin polarization at Ti active sites reconfigures the d‐orbital electron distribution, thereby increasing the density of spin‐polarized electronic states near the Fermi level. Furthermore, Ti 3d‐O 2p orbital hybridization lowers the adsorption energies of H 2 O and O 2 by 2.5‐fold and 1.6‐fold, respectively, thereby facilitating interfacial redox reactions and leading to enhanced ROS generation. Notably, UTN combined with US achieves 86.07% tumor inhibition efficiency. This work establishes novel insights into defect engineering, spin‐state modulation, and surface interfacial adsorption in SCT, providing a theoretical paradigm framework for designing of high‐performance sonocatalysts.