Accurate design of hollow/tubular porous g-C3N4 from melamine-cyanuric acid supramolecular prepared with mechanochemical method

The melamine-cyanuric acid (MA-CA) supramolecular is regarded as an ideal starting material to prepare tubular or hollow g-C3N4. The morphologies of g-C3N4 diversify owing to different preparation condition of MA-CA supramolecular, which is far from satisfactory to be explained by the mechanism of self-templating of precursors during calcination. To disclose the hidden rules of shape variety of g-C3N4 derived from MA-CA, we fabricate MA-CA mixture/supramoleculars with ill-defined morphologies using the mechanochemical technique. After polymerization, the obtained g-C3N4 samples are in the shapes of hollow nanorods (HNR), nanotubes (NT), and porous nanosheets (NS) depending on the hydrogen bonding degree between CA and MA in the starting materials. The photocatalytic activity of these g-C3N4 samples in H2 evolution and organic pollutants degradation increases with the rising of surface areas with the exception of g-C3N4 NS. The relatively lower photocatalytic performance of g-C3N4 NS than hollow and tubular g-C3N4 samples can be attributed to its more positive CB position and worse photogenerated carrier separation ability. The cavity void of hollow and tubular g-C3N4 samples realizes the enrichment of reactive oxygen species and organic pollutants into a local microenvironment, which provides a driving force to facilitate the oxidation degradation of pollutants. This study provides a forceful basis for the systematic fine-tuning of the morphologies and physico-chemical properties of g-C3N4.