Donor–Acceptor Tuning Regulates Viologen Redox Behavior for Selective H2O2 Photosynthesis

Regulating redox-active electron acceptors offers a strategy for directing multielectron photocatalysis beyond conventional charge-separation engineering. Here, we demonstrate substituent-controlled viologen redox regulation in pyrene–viologen porous organic polymers (PyVio-X) for selective H2O2 photosynthesis. Carbonyl functionalization (PyVio-CO) enhances donor–acceptor interactions and charge separation, while facilitating photoinduced viologen radical (V-N+•) formation. PyVio-CO achieves an H2O2 production rate of 1786 μmol g–1 h–1 in pure water under visible light and ambient air, with a solar-to-chemical conversion efficiency of 0.25% and an apparent quantum yield of 4.95%. Mechanistic investigations support sequential O2 reduction involving ·O2– and *OOH intermediates, mediated by reversible V-N2+/V-N+• redox cycling. Enhanced two-electron O2 reduction selectivity and suppressed H2O2 decomposition further promote H2O2 accumulation. This work establishes substituent-controlled redox mediation as a molecular design principle for selective multielectron photocatalysis.