1：Experimental Design and Method Selection:

A one-step solvothermal method was used to synthesize Bi4O5BrxI2?x solid solutions by adjusting the molar ratio of Br/I. This method was chosen for its simplicity compared to multi-step processes.

2：Sample Selection and Data Sources:

Bismuth nitrate pentahydrate, potassium bromide, sodium iodide, and other chemicals were purchased from Shanghai Chinese Medicine Group Chemical Reagent Co., Ltd. Samples were prepared with Br/I ratios of 2:0,

3：

4：5,

1,

5：

6：5, and

7：List of Experimental Equipment and Materials:

Materials included Bi(NO3)3·5H2O, KBr, NaI, NaOH, phenol, RhB, ethanol, polyethylene glycol

8：Equipment included XRD (D8 advance diffractometer), XPS (Thermo Fisher Scientific ESCALAB-250X), SEM (JEOL S4800), TEM (JEM-2100 plus), UV–vis DRS (UV-3600 plus), photocurrent and EIS (Chenhua CHI660E electrochemical workstation), PL (Cary eclipse), BET (ASAP2020 MP instrument), and a 300 W Xe lamp with a 420 nm cut-off filter. Experimental Procedures and Operational Workflow:

4 Dissolve Bi(NO3)3·5H2O in polyethylene glycol 400, add KBr and NaI mixture, adjust pH with NaOH, perform solvothermal reaction at 160°C for 16 h, wash and dry the product. Characterize using XRD, XPS, SEM, TEM, UV–vis DRS, photocurrent, EIS, PL, and BET. Evaluate photocatalytic activity by degrading phenol and RhB under visible light, with sampling and absorbance measurement.

9：Data Analysis Methods:

XRD for phase identification, XPS for elemental analysis, SEM/TEM for morphology, UV–vis DRS for band gap calculation using (αhν)^(1/2) vs. hν plots, kinetic analysis using pseudo-first-order equation -ln(C/C0) = kt, photocurrent and EIS for charge separation efficiency, PL for recombination rate.