Delaminated carbon nitride nanosheets were prepared by high temperature H2 treatment of bulk carbon nitride with defects being introduced during this treatment. Although the defects can act as traps for charge carriers, reducing photoluminescence lifetime, they also form highly active photocatalytic sites for hydrogen evolution. The nanostructured materials exhibit substantially enhanced photocatalytic activity due to a synergistic effect between delamination, the presence of defects and associated band gap changes.