Fabrication of visible-light-driven bulk carbon doped carbon nitride with enhanced photocatalytic activity for tetracycline degradation and mechanism insight

Carbon nitride (CN) has garnered considerable attention in the realm of pollutant treatment. However, the photocatalytic activity of pristine CN is severely restricted due to its limited light absorption and rapid recombination of photoinduced carriers. Herein, a rational configuration of dopant and precursor with similar chemical structure was employed to synthesize C doped CN (CCN) through the copolymerization of 2,4,6-triamine-pyrimidine (TAP) and melamine. The characterization results demonstrate that the incorporation of pyrimidine block from TAP monomer not only realizes nearly homogeneous C doping in bulk, but also controls the doping site accurately. Consequently, it enables the CN to process significant absorption in the visible light region, narrow the intrinsic band gap from 2.73 to 2.53 eV, and enhance separation efficiency of photoinduced carriers. As a result, the CCN as a visible-light-driven photocatalyst shows markedly enhanced photocatalytic activity compared with pristine CN in the degradation of tetracycline. The degradation rate constant of the optimal CCN is almost 6.30 times that of pristine CN under visible light. Moreover, the cyclic experiments reveal the favorable stability of CCN. In addition, & BULL;O2  and h+ responsible for the degradation of tetracycline are demonstrated by trapping experiments and electron spin resonance analysis. The work provides a straightforward and impactful copolymerization strategy to achieve bulk doping and control doping position within the CN framework for ameliorating the photoelectrical properties and photocatalytic activity.