Boron and phosphorus co-doped one-dimensional graphitic carbon nitride for enhanced visible-light-driven photodegradation of diclofenac

In this study, the boron (B) and phosphorous (P) co-doped one-dimensional graphitic carbon nitride (CN) (1D BPCN) photocatalysts with various P loadings have been synthesized by hydrothermal-assisted thermal polymerization method for rapid and efficient photodegradation of diclofenac (DCF) under visible light irradiation. The hydrolysis of melamine produces cyanuric acid during the hydrothermal treatment, and then the layered melamine-cyanuric acid complex serves as the supramolecular unit to form the 1D hexagonal-shaped BPCN after thermal polymerization at 500 °C for 4 h. The B and P heteroatoms can be doped inside the CN framework to form P-N and B-C bonds, resulting in the decrease in electric resistance to accelerate the electron transfer as well as the reduction of hole-electron recombination rate to enhance the photocatalytic activity of BPCN. Addition of 3 mL of phosphoric acid significantly enhances the visible-light-responsive photocatalytic activity of 1D BPCN toward DCF degradation. The photodegradation efficiency and rate of DCF over BPCN is a function of initial DCF concentration, pH and anions. Moreover, the BPCN exhibits an excellent reusability which can be effectively photodegrade DCF for at least 5 consecutive cycles. The reactive species of h⁺ and O₂^−• play an crucial role in the enhanced photodegradation of DCF, and, therefore, the plausible reaction mechanism and pathway for DCF photodegradation over 1D BPCN are proposed. These results clearly demonstrate that the BPCN is a superior visible-light-driven photocatalyst, and can pave a gateway to develop metal-free 1D nanocatalysts for the photodecomposition of emerging pollutants in water and wastewater.