The development of catalysts that effectively activate target pollutants and promote their complete conversion is an admirable objective in the environmental photocatalysis field. In this work, graphitic carbon nitride (g-C 3 N 4 ) microtubes with tunable N-vacancy concentrations were controllably fabricated using an in situ soft-chemical method. The morphological evolution of g-C 3 N 4 , from the bulk to the porous tubular architecture, is discussed in detail with the aid of time-resolved hydrothermal experiments. We found that the NO removal ratio and apparent reaction rate constant of the g-C 3 N 4 microtubes were 1.8 and 2.6 times higher than those of pristine g-C 3 N 4 , respectively. By combining detailed experimental characterization and density functional theory calculations, the effects of N-vacancies in the g-C 3 N 4 microtubes on O 2 and NO adsorption activation, electron capture, and electronic structure were systematically investigated. These results demonstrate that surface N-vacancies act as specific sites for the adsorption activation of reactants and photoinduced electron capture, while enhancing the light-absorbing capability of g-C 3 N 4 . Moreover, the porous wall structures of the as-prepared g-C 3 N 4 microtubes facilitate the diffusion of reactants, and their tubular architectures favor the oriented transfer of charge carriers. The intermediates formed during photocatalytic NO removal processes were identified by in situ diffuse reflectance infrared Fourier transform spectroscopy, and different reaction pathways over pristine and N-deficient g-C 3 N 4 are proposed. This study provides a feasible strategy for air pollution control over g-C 3 N 4 by introducing N-vacancy and porous tubular architecture simultaneously. KEYWORDS: N-vacancy, tubular g-C 3 N 4 , porosity, photocatalytic NO x removal

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Solar‐driven CO2 methanation with water is an important route to simultaneously address carbon neutrality and produce fuels. It is challenging to achieve high selectivity in CO2 methanation due to competing reactions. Nonetheless, aspects of the catalyst design can be controlled with meaningful effects on the catalytic outcomes. We report highly selective CO2 methanation with water vapor using a photocatalyst that integrates polymeric carbon nitride (CN) with single Pt atoms. As revealed by experimental characterization and theoretical simulations, the widely explored Pt−CN catalyst is adapted for selective CO2 methanation with our rationally designed synthetic method. The synthesis creates defects in CN along with formation of hydroxyl groups proximal to the coordinated Pt atoms. The photocatalyst exhibits high activity and carbon selectivity (99 %) for CH4 production in photocatalytic CO2 reduction with pure water. This work provides atomic scale insight into the design of photocatalysts for selective CO2 methanation.