Naphthalimide-porphyrin hybridized graphitic carbon nitride for enhanced photocatalytic hydrogen production

A series of NP/g-C₃N₄ hybrids of graphitic carbon nitride (g-C₃N₄) with naphthalimide-porphyrin (NP) are developed for photocatalytic hydrogen production. Planar naphthalimide-porphyrins are facilely adsorbed onto flexible two-dimensional g-C₃N₄ through π–π stacking. Except for its function as photosensitizer, NP in the hybrid could efficient inhibit the charge recombination by electron transfer from the lowest unoccupied molecular orbital (LUMO) of NP to conduction band of g-C₃N₄, meanwhile facilitate Förster energy transfer from g-C₃N₄ donor to NP acceptor for the efficient overlap of absorption spectrum of NP and emission of g-C₃N₄. As a result, the hybrid 2%NP/g-C₃N₄ containing 2% weight ratio of NP exhibits an impressive photocatalytic hydrogen production rate (HPR) of 2297 μmol g⁻¹ h⁻¹, while pristine g-C₃N₄ shows a HPR of 698 μmol g⁻¹ h⁻¹. Specifically, the performance of 2%NP/g-C₃N₄ is far superior compared with the hybrids of g-C₃N₄ with Zn(II)-tetrakis(4-carboxylphenyl)porphyrin (ZnTCPP) and Zn(II)-tetrakis(4-phenyl)porphyrin (ZnTPP) in photocatalytic hydrogen production under the same conditions.