Modulation of the charge transfer dynamic in amorphous carbon nitride allotropic heterojunctions by an alternation in bridging functional groups for the heptazine- and triazine-based fragments is demonstrated to boost the photocatalytic activity for hydrogen evolution. Pyrimidine-bridged and NH-bridged amorphous carbon nitride allotropic heterojunctions are synthesized by thermal polycondensation of a supramolecular complex. Due to the improved charge separation efficiency and visible-light harvesting ability, both allotropic heterojunctions present more than tenfold enhanced photocatalytic activities for hydrogen evolution compared to the conventional heptazine-based carbon nitride under visible-light illumination. Moreover, the photocatalytic activity of the NH-bridged carbon nitride allotropic heterojunction with type-II charge transfer dynamic is superior to the pyrimidine-bridged one with a Z-scheme characteristic. The findings in this study emphasize that the electronic structure at the heterojunction interface governed by the bridging group greatly influences the charge transfer dynamic and therefore is a crucial factor driving the photocatalytic activity of carbon nitride allotropic heterojunctions.
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