Novel Sn doped BiOCl nanosheets with typical conversion pathways of photocatalytic toluene degradation were constructed by a facile method at room temperature. Display omitted •Novel BOC-Sn was fabricated by a one-step chemical precipitate method.•BOC-Sn exhibits significantly enhanced photocatalytic activity.•BOC-Sn exhibits typical conversion mechanism of photocatalytic degradation toluene. The Sn doped BiOCl (BOC-Sn) nanosheets photocatalyst was fabricated by a one-step chemical precipitate method using BiCl3 and SnCl4·5H2O as precursors. The as-fabricated BOC-Sn was applied to the photocatalytic purification of toluene. The microstructures and physicochemical properties of the samples were systematically characterized by XRD, SEM, TEM, UV–vis DRS, PL, XPS, EPR, photocurrent, EIS, BET-BJH. The in situ FT-IR spectroscopy was used to investigate the adsorption and reaction intermediates of photocatalytic toluene degradation under ultraviolet light irradiation. The photocatalytic reaction mechanism was proposed based on the DFT calculation and ESR results. The results indicate that the doped Sn atoms could promote the light absorption, separation and migration of photo-generated carriers on BOC-Sn. However, the reaction intermediates were benzyl alcohol, benzaldehyde and benzoic acid during the photocatalytic toluene degradation on BOC-Sn, which revealed that BOC-Sn and BOC samples featured different reaction mechanisms. The present work could provide insight into the designed Sn-doped BiOCl nanosheets and photocatalytic toluene degradation mechanisms.