Design and in situ production of a reusable ChCl/TPA@Cu metallic DES using PET electrolysis: An environmentally friendly solvent, electrolyte, CO₂ capture agent, and co-catalyst in electrocatalytic carbonylation of quinazolinediones at Cu electrodes

Urban waste management is confronted with significant challenges, including the accumulation of large volumes of waste, environmental pollution, and the loss of valuable resources. The conversion of waste materials into value-added products through advanced chemical and industrial methodologies offers a sustainable approach to mitigate these issues by reducing landfill dependency, enhancing resource recovery, and delivering both environmental and economic benefits. In the present study, polyethylene terephthalate (PET) bottles were subjected to electrolysis to generate a novel metallic deep eutectic solvent (DES), ChCl/TPA@Cu, which is not only more effective but also recyclable and reusable, highlighting its potential for sustainable applications. This DES was subsequently employed in the presence of isatoic anhydride derivatives 2(a–d) and aniline derivatives 3(a–i), functioning multifariously as an electrolyte, solvent, co-catalyst, and CO₂ trapping agent. Under electro-organic synthesis conditions maintained at 60 °C for 2 h with an applied electric current of 20 mA in the presence of Cu rod cathode and Graphite rod anode, various quinazolinedione derivatives 4(a–l) were obtained with good to excellent yields ranging from 90 % to 97 %. The ChCl/TPA@Cu DES exhibited notable recyclability and stability within this electrocatalytic system. Comprehensive characterization of the DES and the synthesized quinazolinedione derivatives was performed using melting point, Fourier-transform infrared spectroscopy (FT-IR), inductively coupled plasma optical emission spectrometry (ICP-OES), proton and carbon-13 nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR), elemental CHN analysis, thermogravimetric analysis (TGA), density functional theory (DFT), electron paramagnetic resonance analysis (EPR), High-performance liquid chromatography (HPLC) and mass spectrometry. These techniques collectively confirmed the successful synthesis, structural integrity, elemental composition, and thermal stability of the compounds, as well as the purity and compositional homogeneity of the DES system.