Synthesis of Carbon Nitride Semiconductors in Sulfur Flux for Water Photoredox Catalysis

Sulfur-mediated synthesis has been demonstrated as a simple but efficient pathway to control the texture and electronic structure of poly(tris-triazine) based graphitic carbon nitride semiconductors with improved photocatalytic reactivity over the pristine counterpart. Here, we advance this strategy by employing cheap and easily available elemental sulfur as the external sulfur species instead of sulfur-containing precursors for the sulfur-mediated synthesis of polymeric carbon nitride photocatalysts. Characterization results revealed that the multiple thermal condensations of carbon nitride precursors in the hot sulfur flux provided a facile means to promote the formation of graphitic-like carbon nitride conjugated systems, altering the traditional route of thermal-induced self-polymerization of melamine. The textural, electronic, and optical properties of the resultants organic semiconductors was therefore strongly modified to endow the materials with improved physical and chemical properties, as demonstrated by the enhanced photocatalytic activity for water reduction and oxidation under visible light irradiation with wavelength >420 nm. This result again underlines the benefit of a sulfur-mediated approach to construct and manipulate polymeric carbon nitride networks for sustainable applications in catalysis and photocatalysis.