Synthesis and characterization of copper MOF of L-ascorbic acid and its catalytic performance in the organic multicomponent reactions

Abstract

A copper coordinated L-ascorbic acid (Cu@AACP) metal–organic framework was synthesized and characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), wavelength dispersive X-ray spectroscopy (WDX), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The BET method was used to investigate the textural characteristics of Cu@AACP, including surface area, pore diameter and total pore volume. The SEM analysis was used to investigate the morphology and size of Cu@AACP particles. AAS, WDX and EDS techniques were used to investigate the elemental content of Cu@AACP. The TGA analysis was used to investigate the presence of solvents or moisture, thermal stability and organic–inorganic content of catalyst. The FT-IR spectroscopy was used to the characterization of functional groups in the structure of the materials. The XRD pattern was used to investigate the crystalline phase of the catalyst. The results of the analyses confirmed the successful synthesis of copper MOF of L-ascorbic acid (Cu@AACP). The catalytic performance of Cu@AACP was examined in synthesizing of 2, 3-dihydroquinazolin-4(1H)-ones (through condensation of aldehydes and anthranilamide in ethanol at 80 °C) and polyhydroquinolines (through condensation of aldehydes, dimedone, ammonium acetate and ethyl acetoacetate in ethanol at 80 °C). The reaction conditions for the synthesis of 2, 3-dihydroquinazolin-4(1H)-ones and polyhydroquinolines were optimized, where the best results were obtained in ethanol solvent at 80 °C in the presence of 6 mg of Cu@AACP as catalyst. The results show that an improved product yield is obtained between 84 and 95%. Recycle test of the catalyst confirmed that the heterogeneous catalyst exhibited good catalytic stability, efficiency and very high activity in successive runs because of its unique pore network. To show the stability of Cu@AACP nanocatalyst after recycling, the recovered catalyst was characterized by AAS, FE-SEM, EDS and FT-IR techniques.