Acetamide‐ or Formamide‐Assisted In Situ Approach to Carbon‐Rich or Nitrogen‐Deficient Graphitic Carbon Nitride for Notably Enhanced Visible‐Light Photocatalytic Redox Performance

Acetamide- or formamide-assisted in situ strategy is designed to synthesize carbon atom self-doped g-C₃ N₄ (AHCN_x ) or nitrogen vacancy-modified g-C₃ N₄ (FHCN_x ). Different from the direct copolymerization route that suffers from the problem of mismatched physical properties of acetamide (or formamide) with urea, the synthesis of AHCN_x (or FHCN_x ) starts from a crucial preorganization step of acetamide (or formamide) with urea via freeze drying-hydrothermal treatment so that the chemical structures as well as C-doping level in AHCN_x and N-vacancy concentration in FHCN_x can be precisely regulated. By using various structural characterization methods, well-defined AHCN_x and FHCN_x structures are proposed. At the optimal C-doping level in AHCN_x or N-vacancy concentration in FHCN_x , both AHCN_x and FHCN_x exhibit remarkably improved visible-light photocatalytic performance in oxidation of emerging organic pollutants (acetaminophen and methylparaben) and reduction of proton to H₂ in comparison of unmodified g-C₃ N₄ . Combination of the experimental results with theoretical calculations, it is confirmed that AHCN_x and FHCN_x show different charge separation and transfer mechanisms, while the enhanced visible-light harvesting capacity and the localized charge distributions on HOMO and LUMO are responsible for this excellent photocatalytic redox performance of AHCN_x and FHCN_x .