1：Experimental Design and Method Selection:

The synthesis of CuO nanoleaves was accomplished through a sol-gel approach. Nitrogen doped carbon quantum dots were synthesized through a one step hydrothermal method. The composite photocatalyst was fabricated by dissolving the synthesized CuO nanoleaves in distilled water and then adding NCQDs in three different amounts with magnetic stirring.

2：Sample Selection and Data Sources:

The required materials to experimentally synthesize the photocatalyst include copper nitrate Cu(NO3)2, sodium hydroxide (NaOH), citric acid and urea. All these materials were obtained from Sigma Aldrich and were of analytical grade.

3：List of Experimental Equipment and Materials:

Rigaku D/Max 2550 VB/PC XRD machine, JEOL-JAD-2300 SEM, Tecnai F20 TEM and HRTEM, Park NX10 AFM, UV-Vis spectrophotometer Cary 100, Perkin Elmer LS-50B luminescence spectrometer, Bruker Alpha Eco-ATR for FTIR studies, Raman spectrometer with uRAMBOSS Dangoo Optron Co. Ltd.

4：Experimental Procedures and Operational Workflow:

The photocatalytic performance of the synthesized photocatalysts was tested by taking 20 ppm solution of methyl orange (MO) in distilled water as a model dye. 50 mg of the photocatalyst was dispersed in 50 mL of dye solution. The mixture was first stirred in dark for adsorption and then exposed to a solar simulator LCS-100 with an intensity of 100 m W/cm2 (one sun intensity) for 4 h.

5：Data Analysis Methods:

The photocatalytic degradation process is represented by the first order kinetics equation: ln (c? / c) = Kapp t, where c? and c are the initial and the remaining solute concentrations at t=0 and at irradiation time t, respectively.