Ag nanoparticles on arginine-cyanoguanidine functionalized magnetic g-C3N4: A catalyst for nitroaromatic hydrogenation and regioselective click reactions

This study describes the development of a novel hybrid nanocatalyst that was obtained by doping magnetic g-C₃N₄ with Ag nanoparticles and modifying it with arginine and cyanoguanidine (Ag@Fe₃O₄-g-C₃N₄-Arg-CG). Comprehensive characterization of the nanocatalyst using techniques such as FTIR, XRD, SEM, and TGA confirmed its structural and morphological properties. The catalytic efficiency of the synthesized nanostructure was evaluated in two key reactions: the reduction of nitroaromatic compounds and a click reaction for 1,2,3-triazole synthesis. The results demonstrate that Ag@Fe₃O₄-g-C₃N₄-Arg-CG effectively reduced various nitroaromatic compounds to substituted anilines at room temperature using NaBH₄ as the reducing agent. Nitrobenzene reduction did not proceed in aprotic solvents such as acetonitrile, CH₂Cl₂, and dimethylformamide, whereas it exhibited a high reaction yield in protic solvents such as ethanol and water. The highest yield (100 %) was observed in water at 50 °C using H₂O solvent. Additionally, the nanohybrid exhibited significant potential for "green" click chemistry by efficiently synthesizing 1,2,3-triazoles under mild conditions, with low catalyst loading. Its magnetic properties facilitated easy recovery, and the catalyst maintained high activity over six cycles, making it suitable for sustainable applications in organic transformations.