Beyond single pathways: synergistic SET–EnT pathways in visible-light photochemistry

Visible-light-driven single-electron transfer (SET) and energy transfer (EnT) catalysis have historically enabled distinct transformations in organic synthesis, yet recent studies show that combining these manifolds can unlock reactivity and selectivity beyond the reach of either mode alone. SET-EnT synergistic catalysis has thus emerged as a powerful paradigm in which photoexcited catalysts orchestrate sequential or coupled electron- and energy-transfer steps under mild conditions, enabling multistep bond construction in a single operation. This review outlines the conceptual and mechanistic foundations of cooperative SET-EnT reactivity and summarizes representative photocatalysts with emphasis on excited-state redox potentials and triplet energies, thereby providing practical guidelines for catalyst selection in dual-mode systems. The literature is organized by the interplay between SET and EnT, including SET-initiated sequences followed by EnT, EnT-initiated sequences followed by SET, and cases where SET and EnT are coupled without a defined sequence. Collectively, these advances demonstrate how deliberate integration of SET and EnT expands the synthetic utility of visible-light photocatalysis and enables outcomes that are difficult to achieve within a single-manifold framework.