One-pot synthesis of 1,3-oxazine derivatives catalyzed by a green nanocomposite of lacunary phosphomolybdate on TiO2/g-C3N4 under mild solvent-free conditions†

In this research, a new and efficient nanocomposite composed of a heteropolyacid stabilized on mesoporous titanium oxide and graphitic carbon nitride was introduced. The prepared nanocomposite was analyzed and characterized using XRD, FE-SEM, EDX elemental mapping, Raman, TGA, TEM and BET techniques. An investigation of the three-component condensation reaction of aromatic aldehydes, 2-naphthol and urea was carried out using H₃PMo₁₁O₃₉@TiO₂@g-C₃N₄ as a nanocatalyst at 80 °C under solvent-free conditions. As a result of the synthesis of 1,3-oxazine derivatives, short reaction times (5–12 min), mild conditions, high product yields (85–95%), purity, easy preparation, compatibility with the environment, low cost, chemical stability and high selectivity were obtained. Furthermore, it is easy to recover the prepared nanocomposites through filtration, and they can be reused for at least five runs in the reaction without losing their catalytic activities.