Spin-state manipulation via boron doping in facet-engineered hematite enables singlet oxygen production from...

Spin state regulation has emerged as a promising strategy to enhance the catalytic performance of transition-metal catalysts in peroxymonosulfate (PMS) activation. Herein, boron doping and facet engineering were synergistically applied to regulate the spin state of hematite, yielding B-doped hematite nanorods (B-HNRs) and nanocubes (B-HNCs) with highly efficient PMS activation and abundant ¹O₂ production. X-ray absorption near-edge structure (XANES) and ⁵⁷Fe Mössbauer spectra analysis revealed that the boron incorporation resulted in the formation of high spin (HS) Fe(II) species with smaller crystal field splitting energy compared to Fe(III). Density functional theory (DFT) calculations revealed that boron doping enhanced the overlap between Fe 3d orbitals and O 2p orbitals of PMS molecules, thereby facilitating electron transfer between PMS and Fe centers. Compared with B-HNCs, B-HNRs possessing more HS Fe(II) exhibited stronger PMS adsorption, greater OO bond activation, and consequently achieved higher ¹O₂ selectivity (91.6%) and superior catalytic performance. The generated ¹O₂ displayed strong resistance to common aqueous interferences and enabled selective pollutant oxidation. Furthermore, the successful continuous-flow reactor operation demonstrated its practical application potential. This work not only offers an innovative approach for the rational modification of transition-metal catalysts but also deepens the mechanistic understanding of PMS activation at the atomic level.