Nano Double Perovskite NaBaBi 1.97 Eu 0.03 MoO 6 : Synthesis and a Recyclable Catalyst for the Synthesis of Quinoxaline

ABSTRACT The novel europium‐doped nano double perovskite NaBaBi 197 Eu 003 MoO 6 was successfully synthesized by citrate‐assisted sol–gel method and employed for the green synthesis of quinoxaline derivatives as an efficient heterogeneous catalyst. The crystalline structure and physicochemical properties of the catalyst were characterized by x‐ray diffraction, scanning electron microscopy‐energy dispersive x‐ray spectroscopy, Fourier transform infrared spectroscopy, Particle size analyzer, Inductively Coupled Plasma Optical Emission Spectroscopy, and Brunauer–Emmett–Teller surface area analysis. The catalyst possesses a highly crystalline orthorhombic double perovskite structure, a porous nanostructured morphology, a moderate surface area, and uniformly distributed constituent elements. The catalytic activity for condensation of o‐phenylenediamine with phenacyl bromides was investigated under environmentally benign conditions. Systematic optimization showed that 15 mol% catalyst loading in water provided optimum performance, affording quinoxaline derivatives in excellent isolated yields (84%–95%) within 40–45 min at room temperature. The statistical evaluation by one‐way ANOVA and quadratic regression analysis confirmed the reliability of the optimization results (R 2 = 0.963; adjusted R 2 = 0.951; p < 0.0001). The catalyst exhibited a broad substrate scope for both electron donating and electron‐withdrawing substituents and excellent tolerance to functional groups. A plausible catalytic mechanism involves Lewis acid activation by Bi 3+ /Eu 3+ centers and redox‐assisted aromatization by Mo─O active sites. The heterogeneous nature of the catalyst was verified by hot filtration and ICP–OES analysis, which showed negligible leaching of Na, Ba, Bi, Eu, and Mo (<0.05 ppm). The favorable green chemistry metrics (Atomic Efficiency = 67.14%, Reaction Mass Efficiency = 63.78%, E‐factor = 0.568, and Process Mass Intensity = 1.57) confirm that the developed catalytic process is an efficient, low‐waste, and environmentally benign strategy for quinoxaline synthesis. Furthermore, the catalyst presented high catalytic activity for five successive reaction cycles with a minor reduction in the yield of the product, which proved the excellent structural stability and recyclability of the catalyst. NaBaBi 1 . 97 Eu 0 . 03 MoO 6 was identified as a promising heterogeneous catalyst for the sustainable synthesis of biologically important quinoxaline derivatives due to its high catalytic efficiency, green reaction conditions, easy catalyst recovery, and negligible metal leaching.