Solid-Solid Interfacial Synthesis of Atomically Thin Graphitic Carbon Nitride Film

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄): crystalline 2D conjugated polymer an analogy to graphene is an attractive candidate for a metal-free and visible light-responsive photocatalyst. Due to its high specific surface area, various kinds of attempts have been made to fabricate 2D g-C₃N₄. Most of them are based on a top-down method which separates monolayer g-C₃N₄ via chemical or physical exfoliation of layered bulk g-C₃N₄. However, the delamination process causes structural damage which limits the grain size and doping of impurities to exfoliated 2D g-C₃N₄. Thus, bottom-up synthesis methods are desperately demanded for a large scale and impurity free 2D g-C₃N₄ production. Here, we present an entirely new approach using solid/solid interface act as a non-equilibrium reaction field which exclusively promotes 2D polymer conjugation. Melamine (C₃N₆H₆) sandwiched between two solids: a sapphire substrate and Au thin-film was annealed and polymerized to form an atomically thin film of g-C₃N₄. We characterized the stoichiometric composition and morphology of confined conjugated films on a sapphire substrate by XPS and AFM. Ultrathin g-C₃N₄ films have been found resulting from constrained 2D polymer crystallization.