Zr/P Co-Doped TiO₂ Nanophotocatalyst for Green and Rapid Microwave- and Rapid Microwave-Assisted Synthesis of Azlactones

Abstract The development of efficient and sustainable synthetic methodologies is a central goal of green chemistry. In this work, we report the design and application of a novel zirconium/phosphorus (Zr/P) co-doped TiO₂ nanophotocatalyst, synthesized via the sol–gel method, for the rapid and high-yielding microwave-assisted synthesis of azlactones. A series of 2-(4-substituted phenyl)-4-(substituted arylidene)-1,3-oxazol-5-ones (5a–5e) were prepared through the condensation of hippuric acid with substituted aromatic aldehydes in the presence of acetic anhydride and the catalyst. Structural and morphological studies (XRD, FESEM, TEM) confirmed the nanoscale dimensions, uniform dispersion, and enhanced surface area of the catalyst, with crystallite sizes in the 20–35 nm range. Compared to conventional protocols, the microwave-assisted route drastically reduced reaction times (3–5 min vs. 1–2 h) while improving yields (89–96%). The dual doping effect of Zr and P synergistically enhanced charge separation and visible-light activity, enabling superior catalytic performance. This methodology not only improves synthetic efficiency but also aligns with green chemistry principles by minimizing energy input and hazardous reagents. The study demonstrates the promise of Zr/P co-doped TiO₂ nanophotocatalysts as sustainable platforms for organic transformations.