Interlayer Confinement Steers Peracetic Acid Activation Toward Nearly Exclusive Singlet Oxygen Generation

Precisely controlling reaction pathway is vital for selective oxidation chemistry but remains challenging due to the complexity of oxidant–catalyst interactions, especially during activation of peracetic acid (PAA) that offers greater structural flexibility than inorganic oxidants. While various catalyst engineering approaches are available to strengthen PAA nonradical catalysis, they fail to fundamental suppress radicals generation. Here, we propose an interlayer confinement strategy to deterministically reprogram the PAA activation pathway toward singlet oxygen ( 1 O 2 ) generation. By stabilizing atomically dispersed cobalt sites within a KOH‐compressed interlayer space of montmorillonite (MT) nano‐galleries (Co SAC ‐KMT), a deck‐effect‐induced confined microenvironment is constructed to fundamentally alters the PAA‐catalyst interaction. Such confinement suppresses radical‐dominated channels and redirects PAA activation route to nearly exclusive 1 O 2 generation. Mechanistic and theoretical analyses reveal that reduced interlayer spacing reshapes the local PAA adsorption configuration and energy landscape to facilitate 1 O 2 formation. Such a confinement regulation strategy can also be extended to peroxymonosulfate (PMS) activation for efficient pathway modulation, indicating it may serve as a transferable principle to guide Fenton‐like catalyst design. With 1 O 2 ‐dominated pathway, the Co SAC ‐KMT/PAA system demonstrated superior environmental robustness and long‐term stability for real water treatment.