Structures, properties, and applications of two-dimensional C3N and derivatives.

The newly synthesized two-dimensional (2D) carbon nitride with the stoichiometric formula, C3N, has attracted extensive attention due to its unusual properties, including high stiffness, remarkable thermal stability and conductivity, enhanced interfacial chemical activity, and promising applications in energy storage and catalysis. Despite its graphene-like honeycomb lattice, C3N exhibits an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, presenting a disrupted -bond network, charge polarization, and a non-uniform potential surface. In this review, we summarize recent experimental progress and theoretical insights into the electronic, mechanical, thermal, and adsorption properties of 2D C3N and its derivatives, ranging from chemically functionalized C3N, doped C3N, C3N bilayers, and quantum dots to van der Waals heterostructures. We further discuss their potential applications in photocatalysis, electrocatalysis, battery electrodes, gas sensors, and biological systems.