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Retaining the ultrathin structure of two‐dimensional materials is very important for stabilizing their catalytic performances. However, aggregation and restacking are unavoidable, to some extent, due to the van der Waals interlayer interaction of two‐dimensional materials. Here, we address this challenge by preparing an origami accordion structure of ultrathin two‐dimensional graphitized carbon nitride (oa‐C3N4) with rich vacancies. This novel structured oa‐C3N4 shows exceptional photocatalytic activity for the CO2 reduction reaction, which is 8.1 times that of the pristine C3N4. The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects, which leads to modification of the electronic structure, regulation of the CO2 adsorption energy, and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction. This study provides a new avenue for the development of stable high‐performance two‐dimensional catalytic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyridine conjugated graphitic carbon nitride is successfully synthesized. • As-prepared catalyst exhibits superior photocatalytic hydrogen evolution. • Modulated localization of electron cloud density in as-prepared catalyst. • Narrowed bandgap and enhanced carriers' separation efficiency in as-prepared catalyst. High photogenerated carrier recombination and poor visible light response in symmetry graphitic carbon nitride are two classical problems for photocatalytic hydrogen evolution. In this work, we rationally design a novel carbon nitride (DPCN) with asymmetric embeddedness of pyridine ring. The embedded pyridine ring modulates the localization of electron cloud density, resulting in a narrowed bandgap and an enhanced carriers' separation efficiency. They are further confirmed by UV–vis spectra and femtosecond transient absorption (fs-TA) spectroscopy, whose results are consistent with DFT theoretical calculations. This DPCN catalyst shows enhanced photocatalytic hydrogen evolution rate of 180.5 μmol h−1 and the apparent quantum efficiency of 14.6 % at 420 nm, surpassing most reported g-C 3 N 4 -based photocatalysts. This work provides a new sight on designing two-dimensional photocatalysts by modulating the localization of electron cloud density through breaking topological symmetry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Intramolecular heterostructured carbon nitride is successfully synthesized. • The as-prepared sample exhibits superior photocatalytic hydrogen production. • Rapid separation and transfer of photogenerated carriers in as-prepared sample. • The addition of salt mixture regulates the localized electronic structure. Efficient separation and transfer of photogenerated carriers is vital for efficient photocatalytic hydrogen evolution. We report development of a new type of intramolecular heterostructure graphitic carbon nitride with heptazine-triazine (CN-HT) by use of a one-step thermal polymerization method. This intramolecular heterostructure changes the electronic structure to promote charge transfer and enhances the adsorption of H*. The as-prepared CN-HT exhibits superior photocatalytic hydrogen evolution of 88.29 μmol/h, which is 14.2 times that of pristine CN. The apparent quantum yield is 10.1% at 400 nm and 9.6% at 450 nm. The efficient separation and transfer of photogenerated carriers as well as the expanded visible light absorption in this intramolecular CN heterostructure contribute to the efficient utilization of photogenerated carriers, thus enhancing the photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]