Electronic structure engineering of carbon nitride materials using polycyclic aromatic hydrocarbons

The design of charge separation sites under illumination in semiconductors is a standing challenge for their utilization as photo(electro)catalysts. Here, the synthesis of modified carbon nitride materials (CNs) with donor-acceptor (D-A) domains, with altering electronic structure, is reported. To do so, new monomers based on polycyclic aromatic hydrocarbons (PAH)-substituted 1,3,5-triazine were designed, which were then embedded within cyanuric acid-melamine supramolecular assemblies to form CN precursors. The conjugation degree of PAHs was systematically changed, from single benzene ring up to pyrene unit, elucidating the role of the conjugation degree on the morphology, structure and electronic properties as well as photo(electro)catalytic activity. The careful design of the D-A sites results in excellent photocatalytic activity as well as long-term stability for the hydrogen evolution reaction. Moreover, PAH-CNs films exhibit enhanced charge separation, optical absorption, electrochemical surface area and electronic conductivity, leading to an outstanding photoelectrochemical (PEC) activity compared to pristine CN.