Two Ways to more NH2‑Groups: Formation of Polymeric Carbon Nitride via Melem Tetramer Nano Sheets or Supramolecular Assembly of Melamine and Cyanuric Acid for Applications as Photocatalyst

• Published in: ACS applied nano materials 2024-01, Vol.7 (1), p.1402-1415
• Main Authors: Weers, Marco, von Seggern, Aaron R., Vocke, Heinrich, Taffa, Dereje H., Wark, Michael
• Format: Article
• Language: English
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.3c05516

Polymeric carbon nitride (PCN) can be prepared by heating of nitrogen rich precursors and is used as a photocatalyst for hydrogen evolution and transformation of organic molecules. This work gives a deeper understanding of the different properties of PCN and the observed intermediates when melamine or urea are chosen as precursors and heated to temperatures in the range of 350–575 °C. Melem or a melem-tetramer are the main intermediates when melamine is used as starting material, while urea-based PCN is formed via a supramolecular assembly of melamine and cyanuric acid. This leads to crucial differences in properties such as surface area, amount of NH2-groups and photocatalytic activity. PCN from urea, loaded with Pt nanoparticles, shows higher activities for photocatalytic hydrogen evolution due to more NH2-groups. The melem-tetramer shows nanosheetlike structure combined with a high amount of NH2-groups and has the highest activity of all prepared catalysts for the photocatalytic reduction of 5-(hydroxymethyl)­furfural (HMF) to 2,5-bis­(hydroxymethyl)­furan (BHMF). Thus, this research demonstrates the formation mechanism and the design of PCN based catalysts with a large amount of NH2-groups and a high photocatalytic reduction ability.