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[Display omitted] The challenge of mitigating pollution stemming from industrial exhaust emissions is a pressing issue in both academia and industry. This study presents the successful synthesis of nitrogen-defect-enriched graphite carbon nitride (g-C 3 N 4) using a two-step calcination technique. Furthermore, a g-C 3 N 4 -Au heterostructure was fabricated through the photo-deposited Au quantum dots (QDs). When subjected to visible light irradiation, this heterostructure exhibited robust nitric oxide (NO) photooxidation activity and stability. With its fluffy, porous structure and large surface area, the nitrogen-defect-enriched g-C 3 N 4 provides more active sites for photooxidation processes. The ability of g-C 3 N 4 to absorb visible light is enhanced by the local surface plasmon resonance (LSPR) effect of Au QDs. Additionally, the lifetime of photogenerated charge carriers is extended by the presence of N defects and Au, which effectively prevent photogenerated electron-hole pairs from recombining during the photooxidation process. Moreover, the oxidation pathway of NO was analyzed through In-situ Fourier transform infrared (FT-IR) spectroscopy and Density Functional Theory (DFT) calculation. Computational findings revealed that the introduction of Au QDs decreases the activation energy of the oxidation reaction, thereby facilitating its occurrence while diminishing the formation of intermediate products. As a result, NO is predominantly converted to nitrate (NO 3 −). This work unveils a novel approach to constructing semiconductor-cocatalyst heterostructures and elucidates their role in NO photooxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru(III) sites in solid micellar catalyst can be reversible switched to Ru0 clusters. • Ru(III) single-sites selectively catalyze the hydrogenation of functional groups. • Ru0 nanoclusters in contrast are very active for hydrogenating aromatic rings. Traditionally, catalytic active sites are robust; they do not change after a reaction. We show here that the Ru(III) active sites in a solid micellar Ru(III)@MCM catalyst can be controllably switched to Ru0 nanoclusters and vice versa by a mild treatment. The Ru(III) single-sites selectively catalyze the hydrogenation of functional groups such as carbonyl, and double and triple bonds in aromatic compounds via heterolytic H 2 activation. The Ru0 nanoclusters in contrast are very active for hydrogenating aromatic rings. Ru0 nanoclusters are reversibly formed from the Ru(III) sites via hydrolysis and reduction as shown by XAS, HRTEM, CO adsorption, and DFT calculations. The reported strategy offers reversible switching between oxidized and metallic states of Ru to perform different chemical transformations, achieving on-demand active sites. [ABSTRACT FROM AUTHOR]