1：Experimental Design and Method Selection:

The study involved synthesizing BiOIO3/g-C3N4/MoS2 ternary photocatalysts using hydrothermal synthesis for BiOIO3/g-C3N4 and ultrasonic solvent-exfoliation for incorporating MoS2. The design aimed to enhance photocatalytic performance through heterostructure formation and increased active sites.

2：The design aimed to enhance photocatalytic performance through heterostructure formation and increased active sites. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples included BiOIO3/g-C3N4 and BiOIO3/g-C3N4/MoS2 composites with varying MoS2 mass ratios (1:1:

3：1 to

1:0.5). Data were obtained from characterization techniques and photocatalytic experiments.

4：5). Data were obtained from characterization techniques and photocatalytic experiments. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included SEM (LEO 1530VP), TEM (Phillips CM200), XRD (Rigaku D/MAX 3C), XPS (PHI5300), BET (Hitachi F 4600), FT-IR (Nicolet Nexus), UV–vis DRS (Agilent 8453), PL (Edinburgh FLS920), TRPL (Edinburgh Instruments FS5), and a photocatalytic reactor with a 9 W LED lamp. Materials were Bi(NO3)·5H2O, KIO3, urea, ethanol, and bulk commercial MoS

5：Experimental Procedures and Operational Workflow:

BiOIO3 was synthesized hydrothermally, g-C3N4 by calcination, and BiOIO3/g-C3N4 via hydrothermal treatment. BiOIO3/g-C3N4/MoS2 composites were prepared by ultrasonic exfoliation in ethanol. Photocatalytic tests involved dispersing 35 mg catalyst on quartz glass, exposing to visible light after adsorption-desorption equilibrium, and measuring Hg0 removal.

6：Data Analysis Methods:

Data were analyzed using XRD for crystal structure, SEM/TEM for morphology, XPS for chemical states, BET for surface area, FT-IR for functional groups, UV–vis for optical properties, PL/TRPL for charge separation, and efficiency calculations using Eq. (1).