The exploration of efficient and stable composite-materials as nitrogen reduction photocatalysts featuring wide spectrum absorption and nitrogen fixation active sites has become specifically significant. In this work, a series of mixed-addendum PMoV-based organic–inorganic hybrid materials coupled with rich sulfur vacancy 1T MoS₂ (Sv-1T MoS₂) through a hydrothermal growth strategy are presented towards green NH₃ production. The intervalence electron transfer of the reduced polyoxometalates, as well as the construction of a Ni-trinuclear cluster-based framework, is responsible for the capable light-harvesting performance of the well-defined PMo₈V₆–Ni crystalline material, and Sv-1T MoS₂ which serves as a cocatalyst can facilitate electron–hole separation of the light absorbers, which further promotes the ammonia production capacity of the composite materials. As expected, the ammonia generation rate of Sv-1T MoS₂/PMo₈V₆–Ni (80.6 μmol h⁻¹ g⁻¹) is much higher than that of either PMo₈V₆–Ni (9.7 μmol h⁻¹ g⁻¹) or Sv-1T MoS₂ (8.6 μmol h⁻¹ g⁻¹) component. Such a noble-metal-free system therefore shows an apparent quantum efficiency (AQE) of 0.368% at 550 nm. The “working-in-tandem” mechanism established by sulfur vacancies as nitrogen active sites and polyoxometalate crystalline photosensitizers are extremely crucial for facilitating N₂ chemisorption and NH₃ formation. This work provides a fresh perspective for the rational design of photocatalyst composite materials with energetic electrons towards efficient nitrogen fixation.