1：Experimental Design and Method Selection:

A solvothermal method was used to synthesize BiOCl/(BiO)2CO3 composites by varying the ethanol/water volume ratio. Guanidine hydrochloride served as a source of chloride and carbonate ions and as a crystal growth inhibitor.

2：Sample Selection and Data Sources:

Samples were prepared with different ethanol/water ratios (e.g., S(0.45) for 45% ethanol) using bismuth nitrate pentahydrate and guanidine hydrochloride as precursors.

3：45) for 45% ethanol) using bismuth nitrate pentahydrate and guanidine hydrochloride as precursors. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Chemicals included bismuth nitrate pentahydrate, ethanol, guanidine hydrochloride (from Sinopharm Chemical Reagent Co., Ltd). Equipment included autoclave, XRD (Bruker D8 ADVANCE), TEM (JEOL JEM-100C II), SEM (Hitachi S4800), XPS (Kratos AXIS Ultra DLD), UV-vis spectrophotometer (LAMBDA 950), zeta-potential analyzer (Malvern Zetasizer Nano ZS 90), and photocatalytic setup with halogen and mercury lamps.

4：Experimental Procedures and Operational Workflow:

Precursors were dissolved in solvent mixtures, stirred, heated in an autoclave at 180°C for 12 hours, washed, dried, and characterized. Photocatalytic tests involved degrading rhodamine B under visible light with sampling and UV-vis analysis.

5：Data Analysis Methods:

XRD for phase identification, SEM/TEM for morphology, XPS for surface composition, UV-vis for band gap calculation, and kinetic analysis for degradation rates using pseudo-first-order models.