1：Experimental Design and Method Selection:

A facile hydrothermal route was used to synthesize Mn-doped Fe2O3 nanocubes supported on g-C3N4 sheets. The method involved thermal polymerization for g-C3N4 preparation and hydrothermal synthesis for the composite.

2：Sample Selection and Data Sources:

Various mass ratios of g-C3N4 to Mn-doped Fe2O3 (20:1, 10:1, 5:1) were prepared to optimize photocatalytic performance. Pure g-C3N4 and Fe2O3/C3N4 samples were used for comparison.

3：List of Experimental Equipment and Materials:

Chemicals included FeCl3·6H2O, MnCl2·4H2O, PVP, urea, NaAc, ethylenediamine. Equipment included X' Pert Pro XRD system, AXIS Ultra DLD XPS, JEOL JSM-6700 FESEM, JEM-2100 F TEM, Tristar 3010 isothermal nitrogen sorption analyzer, Lambda 750 spectrophotometer, Lambda LS55 PL spectrometer, 300 W Xe lamp, gas chromatograph.

4：Experimental Procedures and Operational Workflow:

g-C3N4 was prepared by heating urea at 550°C in N2. The composite was synthesized by dispersing g-C3N4 in water, adding precursors, and hydrothermal treatment at 200°C for 10 h. Photocatalytic activity was tested in a lab-made reactor with visible light irradiation and gas analysis.

5：The composite was synthesized by dispersing g-C3N4 in water, adding precursors, and hydrothermal treatment at 200°C for 10 h. Photocatalytic activity was tested in a lab-made reactor with visible light irradiation and gas analysis. Data Analysis Methods:

5. Data Analysis Methods: XRD, XPS, FESEM, TEM, BET surface area analysis, UV-vis DRS, PL spectra, photocurrent measurements, and gas chromatography were used for characterization and performance evaluation.