Inducing spin polarization in Cs2CuBr4 by Fe2+ doping for efficient photocatalytic aerobic toluene oxidation

Fe 2+ -doped Cs 2 CuBr 4 induces strong spin polarization, resulting in efficient charge separation. • O 2 is efficiently activated through antiferromagnetic coupling upon spin-polarized Fe 2+ centers. • The optimized Fe-doped Cs 2 CuBr 4 enables highly efficient and selective photocatalytic oxidation of toluene to benzaldehyde. The high thermodynamic stability and spin-forbidden transition of ground-state triplet oxygen ( 3 O 2 ) to reactive species like superoxide radical (•O 2 − ) pose a formidable challenge for the photocatalytic oxidation of toluene. In this work, we introduced Fe 2+ active sites into Cs 2 CuBr 4 to achieve highly efficient and selective photocatalytic oxidation of toluene to benzaldehyde. The magnetic coupling between Fe 2+ and Cu 2+ breaks the intrinsic antiferromagnetic ordering of the lattice, significantly enhancing spin polarization. Crucially, this enhanced spin state not only facilitates the separation of photogenerated charge carriers but also directly drives the otherwise spin-forbidden conversion of 3 O 2 into reactive oxygen species ( e.g. , •O 2 − ). As a result, the Fe-doped Cs 2 CuBr 4 delivers a dramatically improved benzaldehyde production rate of 15.88 mmol g −1  h −1 (86.4% selectivity), far surpassing the pristine Cs 2 CuBr 4 (0.34 mmol g −1  h −1 ). More strikingly, the application of a 50 mT magnetic field triggers an additional boost to 27.23 mmol g −1  h −1 . This work highlights spin-polarization engineering as an effective strategy for advancing the efficiency and selectivity of photocatalytic oxidation systems. Download: Download high-res image (153KB) Download: Download full-size image