Atomic symmetry alteration in carbon nitride to modulate charge distribution for efficient photocatalysis

•A two-step cystine-mediated strategy is developed to alter the symmetry structure of C3N4.•CN-25CYS possesses alkyl groups and nitrogen vacancies.•The distorted arrangements activate n-π* electron transition of carbon nitride.•The spatial separation of oxidation and reduction sites promotes charge separation.•CN-25CYS achieves 9.6-fold and 15.6-fold higher H2 production rates and RhB degradation rates.