In this study, a metal–organic framework (ZIF-8)-derived nitrogen-doped carbon (C-ZIF)-modified g-C3N4 composite was directly prepared by pyrolysis. C-ZIF@g-C3N4 composites with different loadings were prepared by changing the precursor content. The charge transfer process that occurs at the interface of the ZIF-8-derived nitrogen-doped carbon/g-C3N4 heterostructures strongly hinders the recombination of photoinduced electron–hole pairs, thereby effectively enhancing the photocatalytic activity of C-ZIF@g-C3N4. Meanwhile, the unique hierarchical inorganic/organic heterostructure provides an abundance of active sites for photocatalytic reactions. Upon visible-light irradiation, C-ZIF@g-C3N4 with an optimal ratio of g-C3N4 to C-ZIF components exhibits both enhanced photocatalytic activity and excellent separability during the degradation of dye and hydrogen evolution compared to unmodified g-C3N4.
