In this study, S-scheme heterojunction photocatalysts composed of SnO₂ and ZnSn(OH)₆ (ZHS) were synthesized via a one-step hydrothermal method. The resulting ZHS/SnO₂ (ZS) composites exhibited high crystallinity, enhanced light-harvesting capability, and a well-defined interfacial architecture, all of which synergistically facilitated efficient charge carrier separation through an n–n type step-scheme (S-scheme) mechanism. The enhanced photocurrent response confirmed accelerated charge transport, while the broadened absorption range indicated improved photon utilization. Among the composites, the 10 % ZS sample exhibited the highest photocatalytic activity toward nitric oxide (NO) oxidation (76.95 %), with a reaction rate constant of 0.16982 min⁻¹, which is approximately ten times higher than that of pristine SnO₂ (0.01596 min⁻¹) and ZHS (0.01505 min⁻¹), indicating a remarkable enhancement in reaction kinetics. Furthermore, the 10 % ZS composite exhibited excellent selectivity, limiting nitrogen dioxide formation to only 7.36 % while converting 69.59 % of NO into less harmful products. It maintained high photocatalytic efficiency over six successive cycles with negligible performance loss. In addition, mechanistic analysis confirmed that superoxide and hydroxyl radicals, generated through the S-scheme charge transfer pathway, were primarily responsible for the oxidation process. These findings, together with its preserved structural integrity after cycling, highlight the 10 % ZS composite as a robust, efficient, and selective photocatalyst for nitrogen oxides abatement.