Carbon–Sulfur Moiety Induced Molecular Asymmetry in Perylene Diimide for Efficient Photocatalytic Water Oxidation

The efficiency of photocatalytic overall water splitting is largely limited by the inefficient water oxidation reaction. While perylene diimide (PDI)-based photocatalysts show promise for water oxidation, their performance is hindered by rapid charge recombination and sluggish oxygen evolution reaction kinetics. Herein, a symmetry-broken PDI photocatalyst is designed through partially replacing C═OC═ with C═S moiety, which exhibits superior water oxidation performance, reaching an oxygen evolution rate of 5.74 mmol g⁻¹ h⁻¹ under visible light (λ ≥ 420 nm) without a cocatalyst. Further loading Co(OH)₂ as cocatalyst yields an enhanced photocatalytic oxygen evolution rate of 19.19 mmol g⁻¹ h⁻¹, accompanied with an apparent quantum yield of 14.60% at 550 nm. It is revealed that the introduction of C═S moiety breaks the molecular symmetry of PDI, which kinetically facilitates charge separation by generating a strong internal electric field and thermodynamically favors water oxidation by lowering the reaction energy barrier, thereby leading to efficient photocatalytic water oxidation. This study highlights molecular symmetry breaking as a promising strategy for designing efficient supramolecular photocatalysts for solar-to-fuel conversion.