The design of artificial systems that mimic highly evolved and finely tuned natural photosynthetic systems has attracted intensive research interest. A new system was formulated that encapsulates a quinhydrone (QHQ) cofactor in metal-organic hosts based on inspiration from the redox relays of photosystem II. The M6 L3 triangular prism hosts provided a special redox-modulated environment for the cofactor localized within the pocket, and the proximity effects of the host-guest interactions facilitated the formation of charge-transfer complexes that are typically very difficult to form in normal homogeneous systems. Extensive electron delocalization and well-controlled redox potential were induced to decrease the overpotential of the metal sites for proton reduction. The excellent activity and stability of the supramolecular systems allow the tandem reductions being combined to efficiently reduce nitrobenzene using active H-sources from the light activation of water.