Dipole driven interfacial coupling in COF/Bi₂Fe₄O₉ S-scheme heterojunctions greatly boosts PMS activation for...

Activation of peroxymonosulfate (PMS) in photochemical Fenton-like reactions is often hindered by random carrier migration and reactive oxygen species (ROS) evolution. Herein, a series of S-Scheme heterojunction photocatalysts were constructed by integrating structurally isomeric covalent organic frameworks (COFs) with mullite micro-spherical bismuth ferrite (BFO), which enlarges specific surface area and promotes PMS adsorption through inner-sphere complexation. The formed built-in electric field (BIEF) at the interface induces an interfacial band bending, narrows the band gap, and drives the transition-mediated recombination pathway of photogenerated carriers, thereby enabling selective preservation of high-energy carriers. Remarkably, the ortho-configured COF establishes a stronger intrinsic dipole field, which amplifies the interfacial electric field and redirects the ROS evolution toward a strongly oxidative SO₄•⁻-initiated, ¹O₂-dominant pathway. This unique pathway ensures both high efficiency and exceptional selectivity in photodegradation of neonicotinoids (NEOs) and other emerging pollutants with low energy consumption, surpassing many conventional photocatalysts. Our findings offer a dipole-field-mediated strategy for designing high-performance photo-Fenton-like systems, promising robust performance in real wastewater matrices.