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Modifying the microstructure of photocatalysts while simultaneously introducing vacancies has shown significant potential in enhancing their performance for hydrogen production. Herein, a novel tubular mesoporous carbon nitride (TMCN) with nitrogen vacancies was fabricated using a microwave-assisted synthesis strategy, employing melamine-cyanuric acid supramolecular (MC-S) as the precursor. The optimized TMCN exhibited an outstanding H2 production rate, approximately 29 times higher than that of pristine g-C3N4. The N-vacancies serve as sites for reactant adsorption and activation, leading to enhanced delocalization of HOMO-LUMO. Furthermore, the porous structures of TMCN facilitate the reactant diffusion, while its tubular architectures promote the oriented transfer of charge carriers. Crucially, the markedly improved photocatalytic performance of TMCN can be predominantly attributed to the synergistic effects arising from its superior structure and N-vacancy defects. This work opens new possibilities for the simultaneous formation of surface defect states as photocatalytic reaction sites and distinctive structures conducive to charge carrier transport. [ABSTRACT FROM AUTHOR]

Crystalline carbon nitride can potentially manifest heightened light-harvesting efficiency, coupled with proficient charge migration rates, attributable to the diminished count of recombination centers for photoexcited carriers. This phenomenon stems from the extensive π-conjugated framework and the dispersion of π-electrons. This investigation adopts a self-assembly strategy, utilizing hydrogen-bonded bridging melem with cyanuric acid, to yield crystalline oxygen-bridged carbon nitride. The strategic introduction of oxygen doping, positioned at the junction between heptazine units, and the crystalline architecture endow BCN with augmented photocatalytic H2 evolution capacity. This culminates in a H2 production rate under visible light irradiation that surpasses that of pristine BCN by approximately 23.2 times, and an apparent quantum efficiency (AQE) of 13.2% at 420 nm. The confluence of the oxygen-bridging mechanism and crystalline architecture within carbon nitride profoundly augments the partition and migration pace of photoexcited carriers, resulting in the amplified photocatalytic performance of BCN. This strategic paradigm charts a fresh trajectory toward an exponential augmentation of carbon nitride performance, nimbly regulating both crystalline architecture and elemental doping. [ABSTRACT FROM AUTHOR]