1：Experimental Design and Method Selection

CDs were derived from water hyacinth leaves via hydrothermal treatment and combined with g-C3N4 to form composites. The photocatalytic performance was evaluated under natural sunlight irradiation.

2：Sample Selection and Data Sources

Water hyacinth leaves were used as the green source for CDs synthesis. The photocatalytic degradation of 2,4-DCP was monitored using HPLC.

3：List of Experimental Equipment and Materials

Field emission scanning electron microscope (FESEM, Auriga, Zeiss), high resolution transmission electron microscope (HRTEM, Tecnai 20, Philips), X-ray diffractometer (XRD, D8 Advance, Bruker), X-ray photoelectron spectroscopy (XPS, Axis Ultra DLD, Kratos), Fourier transform infrared (FTIR) spectra (Perkin Elmer Spectrum 400), Ultraviolet–visible diffuse reflectance spectra (UV–vis DRS, UV-260, SHIMADZU), Brunauer–Emmett–Teller (BET) surface area analyzer (TriStar II 3020, Micrometrics?), Photoluminescence (PL) spectrophotometer (Perkin Elmer LS 55), Time Resolved Photoluminescence (TRPL, Edinburgh FLS 920).

4：Experimental Procedures and Operational Workflow

CDs were synthesized from WH leaves via hydrothermal treatment. The composites were prepared by mixing g-C3N4 with CDs solution and undergoing hydrothermal treatment. Photocatalytic experiments were conducted under natural sunlight.

5：Data Analysis Methods

The degradation rate was calculated using a first-order kinetic model. The active species in the photocatalytic process were identified using scavenger tests.