Boron-induced Spin-Polarized Defect Complexes towards Efficient Photocatalytic Tetracycline Decomposition and CO2 Conversion

By employing a non-metal doping strategy, we systematically achieved the stabilization and synergistic modulation of both surface defects and spin polarization within the wide-bandgap semiconductor. This platform is crucial for advancing key applications in both environmental remediation and energy conversion. Optimized photocatalytic activity in TiO 2 is achieved by tailoring its electronic structure through a template-assisted route, where boron acids act simultaneously as dopants and mesopore-directing agents. Mechanistically, advanced techniques including PAS, EXAFS, OCPD and DFT calculations reveal spin polarization in TiO 2 arises when interstitial boron pairs with nearby oxygen vacancies to form B–Ov complexes that stabilize vacancy-derived defect states and, via local dipoles and distortion of TiO 6 octahedron, break spin degeneracy near Fermi level (E f ), thereby suppressing spin-allowed recombination and enhancing photocatalytic charge utilization. Notably, employing boron also enables precise control of hierarchical porosity and surface area in metal oxides. The resulting TiO 2-x bearing spin-polarized B–Ov complexes delivers CO from CO 2 at 24 µmol h⁻¹ g⁻¹ with high selectivity and degrades tetracycline under visible light within 2   h (k = 0.016   min⁻¹), which are 6- and 16-fold faster than pristine TiO 2 and TiO 2 -based photocatalysts reported under similar TC degradation conditions. This work presents a significant advance in the methodology for constructing next-generation free-standing photocatalysts.