One-step green synthesis of carbon-doped graphitic carbon nitride as a catalyst for the enhanced NaBH4-assisted catalytic reduction of methylene blue

The development of efficient wastewater treatment technologies for removing organic pollutants from the textile industry effluents remains a critical global challenge. Therefore, in this study, we explored the catalytic reduction of methylene blue using carbon-doped graphitic carbon nitride (C-g-C 3 N 4 ) as a simple, effective, and sustainable approach. Carbon doping was achieved through a facile imidazole-assisted synthesis, with the level of doping in the material controlled by varying the imidazole concentration introduced during the polycondensation reaction, ranging from 2 to 5 wt%. The resulting materials were thoroughly characterized using various techniques. The catalytic reduction efficiency of the materials was evaluated for the degradation of methylene blue in the presence of sodium borohydride (NaBH 4 ). The XRD pattern showed two peaks–17.4° and 27.6° for pristine g-C 3 N 4 and 17.3° and 27.5° for C-doped g-C 3 N 4 -which are indexed to the (1 0 0) peak of triazine unit and the (0 0 2) peak associated with interlayer stacking. The bandgap energies of pristine g-C 3 N 4 and 3C-doped g-C 3 N 4 were 2.47 eV and 2.37 eV, respectively, with a redshift in the absorption edge, indicating modified electronic properties. The materials g-C 3 N 4 , 2C-g-C 3 N 4 , 3C-g-C 3 N 4 , 4C-g-C 3 N 4, and 5C-g-C 3 N 4 catalysts demonstrated degradation efficiencies of 77 %, 90.9 %, 92.9 %, 88.4 % and 89.4 %, respectively. This study demonstrated a green, imidazole-assisted synthesis of carbon-doped graphitic carbon nitride, combining sustainable processing with engineered electronic and surface properties for effective NaBH₄-assisted catalytic reduction of methylene blue for advanced wastewater treatment. • Defects were introduced into graphitic carbon nitride by polycondensation of urea with imidazole. • XRD and FTIR spectra confirmed the C-doping in the graphitic carbon nitride • The doped graphitic carbon nitride (3C-g-C 3 N 4 ) showed morphological characteristics that were consistent with improved porosity. • The doped graphitic carbon nitride showed improved activity for NaBH 4 -induced reduction of methyl orange. • Thermodynamic calculations showed the feasibility of the reaction was enhanced in the presence of the defected catalysts.