Graphene-like g-C₃N₄ nanosheets (NSs) have been successfully synthesized with a modified polymerization process of melamine by cocondensation with volatile salts. Volatile ammonium salts such as urea–NH₄Cl/(NH₄)₂SO₄/(NH₄)₃PO₄ were added with melamine to modulate the thermodynamic process during polymerization and optimize the structure formation in situ. The surface area, surface structure, and surface charge state of the obtained g-C₃N₄ NSs could be controlled by simply adjusting the mass ratio of the melamine/volatile ammonium salt. As a consequence, the g-C₃N₄ NSs exhibited much higher activity than bulk g-C₃N₄ for the photocatalytic degradation of target pollutants (rhodamine B, methylene blue, and methyl orange), and it also exhibited greater hydrogen evolution under visible light irradiation with an optimal melamine/volatile ammonium salt ratio. The as-prepared g-C₃N₄ NSs with melamine–urea–NH₄Cl showed the highest visible light photocatalytic H₂ production activity of 1853.8 μmol·h^–1·g^–1, which is 9.4 times higher than that of bulk g-C₃N₄ from melamine. The present study reveals that the synergistic effect of the enhanced surface area, surface structure, and surface charge state is the key for the enhancement of photocatalytic degradation and hydrogen evolution, which could be controlled by the proposed strategy. The result is a good explanation for the hypothesis that adding properly selected monomers can truly regulate the polymerization process of melamine, which is beneficial for obtaining g-C₃N₄ NSs without molecular self-assembly. Considering the inexpensive feedstocks used, a simple synthetic controlling method provides an opportunity for the rational design and synthesis, making it decidedly appealing for large-scale production of highly photocatalytic, visible-sensitizable, metal-free g-C₃N₄ photocatalysts.

In this study, a series of ethylene glycol modified urea–melamine–formaldehyde resins were synthesized, and then incorporated into rigid polyurethane foams as a reactive-type liquid flame retardant.

In this work, ethylene glycol-modified melamine–formaldehyde resin (EMF) was synthesized from ethylene glycol, paraformaldehyde, and melamine, and then rigid polyurethane foams (RPUFs) were prepared using EMF, polyols and polyisocyanate. The effects of ammonium polyphosphate (APP) and dimethyl methylphosphonate (DMMP) on the flame retardancy, mechanical properties, thermal stability, and morphology of the prepared RPUFs were studied. It is shown that the flame-retardant performance of EMF-filled RPUFs can be enhanced by the addition of APP and DMMP. Thus, APP and DMMP can synergistically improve the flame retardancy of RPUFs. APP has good smoke suppression, while DMMP can increase the total smoke production and CO/CO₂ weight ratio during the combustion of RPUFs.