摘要： Owing to its low separating and utilizing efficiency of photo-generated charges in the bulk, the application of photocatalytic technique has been restricted for decades. In this paper, based on interlayer ion-exchange between BiOBr0.75I0.25 layers, we demonstrated a specific interfacial process of photocatalytic Cr(VI) reduction by a direct bulk-charge transfer. The results showed that Cr(VI) was effectively converted to nontoxic Cr(III), even under neutral conditions (pH = 7.0). According to ultraviolet-visible spectroscopy (UV-Vis), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, the CrO4 2? anion was readily intercalated into the anion lattice layer of BiOBr0.75I0.25 by ion-exchange with OH? in the interlayer, forming a =Bi-O-CrO3 ? complex. Electron paramagnetic resonance (EPR) and photoelectron-chemistry measurements further revealed that excitation of =Bi-O- CrO3 ? by irradiation was crucial for photocatalytic detoxification of Cr(VI) under pH 7.0. The excitation of =Bi-O-CrO3 ? in BiOBr0.75I0.25 strengthened the bulk-charge transfer as follows: (i) electron transfer from O-II to CrVI produced CrV and O-I, respectively, via ligand-to-metal charge transfer excitation; and (ii) electron injection from BiOBr0.75I0.25 to [=Bi-O?I-CrVO3 ?]* (or exportation hole to valence band) resulted in the reduction of Cr(V) to Cr(III). After that, the newly formed Cr(III) in the interlayer of BiOBr0.75I0.25 was de-intercalated into solution due to the space charge repulsion between Cr3+ and Bi2O2 2+ slab, resulting in stable Cr(VI) reduction performance in a wide pH range from 2.0 to 7.0.