Reprogramming the Fate of Stored Excitation Energy in Persistent Phosphors for Dark Photocatalysis

Solar-driven CO₂ reduction is fundamentally constrained by the intermittency of sunlight, resulting in a temporal mismatch between energy harvesting and catalytic conversion. Persistent phosphors offer a unique platform to bridge this gap by storing excitation energy; however, this stored energy is predominantly dissipated via radiative recombination rather than being utilized as chemically accessible redox power. Here, we demonstrate that the fate of stored excitation energy can be reprogrammed in persistent phosphors, enabling chemical reactions to proceed in the absence of light. By constructing single-crystalline Sr₂MgSi₂O₇:Eu²⁺, Dy³⁺ platelets with co-exposed {100} and {001} facets, anisotropic surface potentials enforce directional charge separation and spatially separated carrier localization, enabling the formation of a long-lived electron reservoir. These stored electrons are subsequently extracted through Pt cocatalyst sites to drive sustained CO₂-to-CH₄ conversion in complete darkness for over 8 h, maintaining a high CH₄ selectivity of 93.6%. This work establishes a general strategy for reprogramming the fate of stored excitation energy, thereby redefining the role of persistent phosphors from luminescent materials to platforms for sustained chemical reactivity beyond illumination.