Sulfur-doped graphitic carbon nitride decorated with starch, Fe₃O₄, and Ag nanoparticles: As efficient and magnetic recoverable nanocatalyst for hydrogenation of nitroaromatics in aqueous media

The reduction of nitroaromatics to corresponding anilines in the presence of the metal catalyst is an important and useful synthetic way in various applications. Silver nanoparticles have recently attained very interest as effective catalysts in the reduction of nitroaromatics by NaBH4. In this study, in situ sulfur-doped graphitic carbon nitride, exhibited as S-g-C3N4, was prepared, employing thiourea as an inexpensive precursor via a simple thermal method and applied as ideal catalyst support. Ag nanoparticles were stabilized on magnetic S-g-C3N4 modified with starch (S-g-C3N4/starch-Fe3O4-Ag). Several spectroscopic and microscopic methods approved the formation of S-g-C3N4/starch-Fe3O4-Ag nanocatalyst and the results have been well interpreted in this context. Sg-C3N4/starch-Fe3O4-Ag presented a good catalytic activity for the reduction of aromatic compounds bearing the nitro group when NaBH4 was employed as the reductive agent. The reduction efficiency of 4-nitroaniline in an aqueous medium was obtained at 99% in the presence of 5 mg of catalyst at 50 C for 90 min. This prepared nanocatalyst's good catalytic potency and stability can be attributed to the synergistic interaction between very dispersed Ag nanoparticles and support.