Structural and optical properties of O-doped and Molecular Terminal Phenyl Grafted g-C3N4 microspheres

Nanostructured g-C3N4 was prepared by a simple one-step method, and O doping and molecular terminal phenyl grafting were achieved by precursor processing. Using melamine (MA) and cyanuric acid (MC) as raw materials, supramolecular precursor is self-assembled from MA and MC molecules in the presence of dimethyl sulfoxide (DMSO) solution. l-phenylalanine (L-PHE) added at the same time not only serves as the sources of O dopant and phenyl in g-C3N4 micro-spheres, but also plays an important role in promoting more complete microsphere structure of g-C3N4 through the morphology regulation of the precursor. Then, O atoms are doped by substituting N atoms in g-C3N4 molecules, and phenyl is grafted at the terminals of g-C3N4 molecules simultaneously. Therefore, the introduction of L-PHE in precursor plays three promoting roles on the final g-C3N4 as a photocatalyst: morphology regulation, O doping and phenyl grafting. The microsphere structure composed of thin nanosheets greatly increases the number of reaction sites in photocatalytic degradation reactions. O dopant acts as a donor in g-C3N4 and provides more additional electrons for the generation of active groups in photocatalysis. The grafted phenyl in g-C3N4 molecules serves as midgap states (MS), and promotes the separation of photo-generated electrons and holes, thus prolonging the lifetime of excitons and allowing more photo-generated carriers to participate in photocatalytic degradation reactions. In addition, the cycle photocatalytic performance stability test results show that the modified g-C3N4 sample shows good stability and light corrosion resistance, and exhibits a practical application prospect.