Design and application of a magnetically recoverable citric acid-functionalized graphene oxide nanocomposite for ultrasound-assisted green synthesis of naphthopyrimidines

This study reports the synthesis of a novel acidic and magnetic nanocatalyst based on graphene oxide (GO), iron oxide (Fe₃O₄), and silica (SiO₂), functionalized with citric acid (CA), which was successfully synthesized and characterized by FT-IR, XRD, SEM, TEM, EDX, TGA, VSM, and Raman spectroscopy. The resulting nanocomposite (GO/Fe₃O₄@SiO₂@CA) exhibited a well-defined core-shell structure, high thermal stability, and superparamagnetic properties. This material was employed as a recyclable and green catalyst for the one-pot multicomponent synthesis of naphthopyranopyrimidines derivatives in ethanol under ultrasonic conditions. The catalyst showed excellent efficiency, product yields (88-97%) within remarkably short times (10-20 min), and was easily recoverable by an external magnet. Additionally, it was able to retain its catalytic activity over seven consecutive cycles with negligible loss in performance. These results highlight GO/Fe₃O₄@SiO₂@CA as a sustainable and high-performance nanocatalyst for green organic synthesis. In this study, we synthesized a mild, non-toxic, green, and multi-acid catalyst, and were able to increase the product formation efficiency and reduce the time with cavitation energy. It seems that this catalyst has the potential to be used for the preparation of other one-pot products.