Mechano-photoexcitation for organic synthesis using mechanoluminescent materials as photon sources

Implementing photochemical reactions through mechanochemical methods can reduce waste generation by eliminating the need for bulk solvents. The absence of solvent results in exceptionally high concentrations of catalysts and reactants in reactions, substantially improving reaction rates and efficiency in terms of both time and energy utilization. However, the integration of mechano- and photochemical approaches is often hindered by the limited transparency of mechanochemical reaction vessels. Here we present a mechano-photoexcitation strategy that utilizes mechanoluminescent materials, in particular SrAl₂O₄:Eu²⁺/Dy³⁺, as internal photon sources activated by mechanical energy. We demonstrate the efficacy of this strategy in two photochemical processes: the Hofmann–Löffler–Freytag reaction and the activation of electron donor–acceptor complexes in sulfonylation reactions. Mechanistic studies confirm the radical nature of these transformations, and control experiments validate the critical role of mechano-photoactivation. By utilizing mechanical energy alone, this method eliminates the need for external light sources and enables gramme-scale photochemical transformations. Our approach represents a valuable application of mechanical energy in synthetic chemistry, providing a complementary means for integrating photochemistry with mechanochemistry.