Polymeric carbon nitride (PCN) is emerging as promising visible‐light photocatalyst but remains a challenge in greatly improving its photocatalytic activity. The superiority of multiscale porous nanostructures in mass transfer, active site exposure, solar energy harvesting, and rates of reactions are verified in achieving superior photocatalytic activity; however, hierarchical porous PCN microspheres with macropores and mesopores simultaneously are rarely reported in the literature to date. Herein hierarchical macroporous–mesoporous PCN microspheres (HM‐PCNs) are presented for highly enhanced photocatalytic hydrogen production via an in situ precursor transformation technique. Utilizing the solubility difference between cyanamide and dicyanadiamide in aqueous solution, the in situ transformation of PCN precursor from cyanamide to dicyandiamide along the wall surfaces of the hierarchical porous SiO₂ microspheres can produce robust HM‐PCNs with both hierarchical macro–mesopores structure and narrow bandgap (1.88 eV). The obtained HM‐PCNs present enhanced light absorption, promoted charge separation and transfer, and thus demonstrate highly enhanced hydrogen evolution activity (4635.8 µmol h⁻¹ g⁻¹) by a factor of 31.7 over the pristine PCN. Ab initio calculations indicate that C atoms at the outmost positions of the pores greatly reduce the bandgap and facilitate the electron–hole separation.

中文翻译：

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具有窄带隙的层级宏观–介孔聚合物氮化碳微球增强了光催化氢的产生

聚合氮化碳（PCN）逐渐成为有前途的可见光光催化剂，但在大大提高其光催化活性方面仍然是一个挑战。多尺度多孔纳米结构在传质，活性位点暴露，太阳能收集和反应速率方面的优越性已得到证实，可实现优异的光催化活性；然而，迄今为止在文献中很少报道同时具有大孔和中孔的分级多孔PCN微球。本文介绍了通过原位前体转化技术高度增强光催化制氢的分级大孔-中孔PCN微球（HM-PCN）。利用氰胺和双氰胺在水溶液中的溶解度差异，_2个微球可以产生具有层次化宏介孔结构和窄带隙（1.88 eV）的坚固的HM-PCN。所得的HM-PCNs增强了光吸收，促进了电荷的分离和转移，因此，与原始PCN相比，其析氢活性（4635.8 µmol h ^-1 g ^-1）大大提高了31.7倍。从头算计算表明，孔最外侧的C原子极大地减小了带隙并促进了电子-空穴的分离。