A green, recyclable COF-366 SPE electrode and Ni/urea metallic DES electrolyte to prevent Ni NPs loss in electro-organic Sonogashira carboxylation coupling

Abstract

One of the major challenges in chemical and electrochemical processes is the corrosion and leaching of metal NPs, in addition to the widespread use of hazardous solvents and reagents that may ultimately be released into the environment and wastewater streams. These issues not only increase production costs but also significantly elevate wastewater treatment expenses and environmental burdens. To overcome these limitations, a sustainable electrocatalytic system based on COF-366 and a Ni/urea metallic deep eutectic solvent (MDES) was designed. The developed MDES represents a cost-effective alternative for both precious and earth-abundant metals, such as Ni and Cu. In this electrocatalytic platform, MDES serves multifunctionally as the solvent, electrolyte, catalyst, and co-catalyst. Meanwhile, COF-366, owing to its high specific surface area and porous structure, acts as a CO gas trap and promotes the exchange of Ni ions with MDES. This synergistic interaction enhances catalytic stability, suppresses metal leaching, and prevents the migration of metal species into the environment. The proposed system is reusable, operates under solvent-free or non-hazardous conditions, and effectively prevents the release of metal NPs, solvents, and reagents into the environment, thereby complying with the principles of green and sustainable chemistry. The catalytic performance of this system was evaluated in the electrochemical Sonogashira carboxylation coupling reaction under mild conditions (room temperature, 1.5 h, 12 mA). The methodology afforded good to excellent yields (90–98%) for the synthesis of 1,3-diphenylprop-2-yn-1-one derivatives 4(a–l). COF-366, MDES, and the synthesized products were comprehensively characterized by ¹H NMR, ¹³C NMR, FT-IR, SEM, EDS, CV, TGA, BET surface area analysis, XPS, CHN elemental analysis, and melting point determination.