1：Experimental Design and Method Selection:

The study involved synthesizing g-C3N4 from urea treated with solvents (methanol, ethanol, ethylene glycol) via solvothermal treatment at 75°C for 12 hours, followed by thermal condensation at 550°C for 6 hours. Characterization methods included XRD, FTIR, SEM, BET surface area analysis, UV-Vis spectroscopy, and photoluminescence spectroscopy. Photocatalytic activity was evaluated by degrading methyl orange and reducing Cr(VI) under a 300 W xenon lamp.

2：Sample Selection and Data Sources:

Urea was used as the precursor, treated with solvents; melamine-derived g-C3N4 was used for comparison. Samples were designated based on solvent treatment (e.g., EtCN for ethanol-treated).

3：List of Experimental Equipment and Materials:

Equipment included a furnace for thermal condensation, XRD diffractometer (Bruker D8 advance), FTIR spectrometer (Bruker Tensor 27), SEM (Hitachi S-4800N), BET apparatus (Micromeritics ASAP 2020), UV-Vis-NIR spectrometer (Hitachi U-3900), spectrofluorometer (Horiba Spex Fluorolog-3), photomultiplier (Hamamatsu R928-type), xenon lamp (300 W), and magnetic stirrer. Materials included urea, methanol, ethanol, ethylene glycol, methyl orange, K2Cr2O7, deionized water.

4：Experimental Procedures and Operational Workflow:

Precursor treatment, thermal synthesis, washing, drying, characterization, and photocatalytic testing with specific conditions (e.g., 0.25 g catalyst in 230 mL solution, 10 cm distance from light source).

5：25 g catalyst in 230 mL solution, 10 cm distance from light source). Data Analysis Methods:

5. Data Analysis Methods: Kinetics analysis using pseudo-first-order and zero-order models, Williamson-Hall and Scherrer methods for crystallite size and strain, Tauc plot for band gap, and statistical fitting of data.