Loofah-like carbon nitride sponge towards the highly-efficient photocatalytic transfer hydrogenation of nitrophenols with water as the hydrogen source

The vigorous development of photocatalytic water splitting technology has laid the foundation for the photocatalytic transfer hydrogenation of organic substrates to produce the high value-added chemicals using water as hydrogen source. Nevertheless, the high dissociation energy of the O–H bond impedes its academic progress and the practical applications. Herein, we synthesize a 3D hierarchical porous loofah-like carbon nitride sponge (LCN) with ultrathin thickness via the supramolecular pre-organization coupling with the oxidation etching process, in which the heterogeneous oxygen atoms and the nitrogen vacancies are in-situ engineered. On top of the adorable photocatalytic H₂ evolution (4812 μmol h⁻¹ g⁻¹), LCN associated with Pt cocatalyst reveals a conversion rate of 96.5 % towards the hydrogenation of 4-nitrophenol, substantially superior to the reference experiment (8.3 %). Further based on the isotope-labeling tests and the density functional theory calculations, the photo-generated H⁰ from water is clarified to be the direct reducing agent, tactfully skipping the hydrogen extraction step in the traditional path. This work provides a green and sustainable methodology to transfer the solar energy to the valuable fine chemicals, as well as highlights the importance of the 3D hierarchical porous structure to the catalytic activity.