Engineering Tubular g-C₃N₄ Architectures for Surface-Driven Photocatalysis: A Critical Survey

Tubular g-C₃N₄ represents an attractive structural motif for sophisticated photocatalytic applications, a merit derived from its multiscale pore configuration that accelerates reactant diffusion, the influence of quantum size effects on its electronic bands, which refines photoexcited carrier kinetics, and the oriented charge movement enabled by its distinctive geometric asymmetry. This review not only consolidates recent breakthroughs in synthesis methodologies spanning template-directed and template-free routes, which precisely engineer tube dimensions, wall thickness, and compartmentalization, but also critically analyzes how each modification strategy, including morphological control, elemental doping, defect engineering, and heterojunction construction, concurrently enhances specific surface area, broadens light absorption range, improves carrier mobility, increases active site density, strengthens redox capability, promotes photo-Fenton efficiency, and prolongs carrier lifetime, thereby significantly boosting photocatalytic performance. Future efforts must address scalable green synthesis, atomic-level strain engineering, and operando mechanistic studies to accelerate industrial deployment of these multifunctional materials.