Synergistic •OH/•O2⁻/1O2 radical cycling driven by H2O2 photolysis for base-free glycolic acid production from glycerol

The valorization of crude glycerol, a major byproduct of biodiesel production, into high-value chemicals is critical for sustainable biorefineries. Herein, we report a novel alkali-free and homogeneous photocatalytic strategy for selectively converting glycerol to glycolic acid (GLYA) and formic acid (FA) using H 2 O 2 as a radical initiator under 365 nm UV irradiation. By optimizing volume fraction of H 2 O 2 (3.18％), light intensity (10 W), and temperature (35 °C), 99.3 % glycerol conversion with 23.47 % GLYA yield and 22.66 % FA yield was achieved within 2 h at ambient pressure. Crucially, scavenging experiments, post-illumination reactivity studies and the electron paramagnetic resonance (EPR) spectra revealed a synergistic •OH /•O 2 ⁻/ 1 O 2 radical cycle triggered by H 2 O 2 photolysis: (1) •OH initiates glycerol oxidation to glyceraldehyde; (2) •O 2 ⁻ (generated from O 2 reduction or H 2 O 2 decomposition) produces 1 O 2, which drives selective C-C cleavage to GLYA; (3) •OH/•O 2 ⁻/ 1 O 2 cycle enables mutual regeneration of active species, sustaining oxidation even after light cessation. This autocatalytic cycle eliminates the need for strong bases or noble metals, offering a green, energy-efficient route for glycerol upcycling.