Preparation, characterization, and catalytic activity of Ca2CuO3/CaCu2O3/CaO nanocomposite as a novel and bio-derived mixed metal oxide catalyst in the green synthesis of 2H-indazolo[2,1-b]phthalazine-triones

•Novel Ca2CuO3/CaCu2O3/CaO nanocomposite was synthesized and characterized.•These multi-metal oxides were characterized by XRD, EDX, TGA, FESEM, and TEM.•Eggshell wastes were used as a green source of Ca.•Synthesis of 2H-indazolo[2,1-b]phthalazine-triones in a green and efficient manner•High catalytic activity and reusability of CaO–CuO system as heterogeneous catalyst

As a novel and heterogeneous catalyst, the Ca2CuO3/CaCu2O3/CaO nanocomposite was synthesized via coprecipitation and thermal decomposition methods using CuSO4 and eggshell wastes as inexpensive starting materials. The catalytic activity of the mesoporous mixed metal oxide in the synthesis of 2H-indazolo[2,1-b]phthalazine-triones was investigated. The reaction proceeds to completion within 5–20 min with yields of 80–94%. The suggested strategy for synthesizing 2H-indazolo[2,1-b]phthalazine-triones is of great interest because a novel, green, and low-cost mixed metal oxide is used as a heterogeneous catalyst, on account of its convenient preparation, short reaction time, and high reusability without any loss of catalytic activity.

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