Water-Modulated Construction of Nanoclay/g-C3N4 Heterostructures for Selective Generation of Singlet Oxygen in Peroxymonosulfate Activation Processes

Singlet oxygen (¹O₂), a highly selective oxidant in advanced oxidation processes, remains challenging to generate efficiently and exclusively due to competing radical pathways. Here, we report a water-modulated interlayer confinement strategy for constructing nanoclay/g-C₃N₄ heterostructures (RT/CN) that promote selective ¹O₂ production through tailored interfacial electronic modulation. By precisely tuning the rectorite-to-water ratio during precursor grinding, urea undergoes confined polymerization within the RT interlayers, forming ultrathin g-C₃N₄ nanosheets covalently anchored via Si–N–Al linkages. This asymmetric interfacial architecture induces localized electron redistribution, enabling peroxymonosulfate (PMS) activation through an oxidative, nonradical pathway while fully suppressing radical generation. The optimized RT/CN-H3 catalyst achieves dual-mode ¹O₂ production: interfacial electron transfer under dark conditions and hole-mediated enhancement under visible light. Remarkably, it delivers 96% degradation of Orange II in 30 min (k = 0.102 min^–1) under dark, with near-exclusive (∼100%) ¹O₂ selectivity. This scalable, metal-free platform demonstrates robust reactivity across diverse pollutants and environmental conditions. The work establishes a generalizable strategy for harnessing the interlayer confinement of natural minerals, with broader implications for sustainable oxidation chemistry, environmental remediation, and the rational design of green catalytic systems.