Many experimental studies have demonstrated that exfoliating layered polymers into nanosheets and introducing planar groups into the conjugated polymers were beneficial for improving the photocatalytic activity , as exfoliation reduces the path length to the surface and conjugation fosters higher mobilities . The most widely studied 2D polymers for photocatalysis are nanosheets of graphitic carbon nitrides . Various reviews have discussed the structure, synthesis and photocatalytic performance of carbon nitrides for water splitting . However, the slow surface reaction kinetics, fast charge recombination and low carrier mobility have limited their applications as high efficient photocatalysts . Co-catalysts were usually employed to improve their photocatalytic performance .