Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-value-added chemicals, but it is hampered by sluggish charge dynamics and limited redox potential. Herein, a porous S-doped carbon nitride (S-C₃N_4−y) foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular self-assembly strategy. The S dopants and N vacancies synergistically adjusted the band structure, facilitating light absorption and enhancing the oxidation ability. Moreover, the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer. Consequently, S-C₃N_4−y foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution (4960 μmol/(h·g)) and benzylamine oxidation to N-benzylidenebenzylamine (4885 μmol/(h·g)) with high selectivity of > 99 %, which were approximately 17.6 and 72.9 times higher than those of bulk CN, respectively. The photocatalytic coupling pairing reaction promotes the water splitting by consuming H₂O₂, thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines. This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.