Molecular-Level π-Stacking Engineering in Dative B←N Frameworks for Superior Photocatalytic H₂O₂ Production

The photocatalytic synthesis of hydrogen peroxide (H₂O₂) from O₂ and H₂O represents a sustainable alternative to the energy-intensive anthraquinone process. However, achieving efficient photocatalysis requires precise control over structure-activity relationships, which remains a significant challenge. Herein, we report a molecular engineering strategy that leverages precise tuning of intermolecular π-stacking in three single-crystalline dative B←N frameworks (BNF-75, -76, and -77). By systematically modulating the planarity of the B-acceptors, we achieved a progressive decrease in the root-mean-square deviation (RMSD) of the B-acceptors from 0.463 Å in BNF-75 to 0.201 Å in BNF-77. The BNF-77 exhibits broadened visible-light absorption, enhanced charge separation and transport, and an outstanding H₂O₂ production rate of 5684.6 µmol·g^-1·h^-1 under visible light without sacrificial agents or metal cocatalysts (λ > 420 nm). Simple mechanical grinding for particle-size reduction further elevates the rate to a remarkable 9451.0 µmol·g^-1·h^-1, positioning BNF-77 among the top-performing crystalline photocatalysts based on dative B←N bonds. Integrated mechanistic studies reveal a synergistic mechanism: the dative B←N bond extends light harvesting and promotes charge separation, while the engineered tight π-stacking constructs efficient charge-transport highways and facilitates the two-electron oxygen reduction reaction (ORR) pathway, with superoxide radicals (•O₂ ^-) as the key intermediate.