Copper-supported thiol-functionalized cellulose as a paper-based catalyst for imine synthesis

This study presents an appealing approach to sustainable catalysis using cellulose filter paper as a support for copper-catalyzed reactions. The paper was functionalized with thiol groups through a reaction with thioglycolic acid, which served a dual purpose: partially reducing Cu(II) to Cu(I) and stabilizing active copper species via Cu–S interactions. Spectroscopic analysis confirmed the formation of highly dispersed multi-valent Cu2O/CuO on the thiol-functionalized cellulose, resulting in a highly efficient copper catalyst. This catalyst demonstrated excellent performance in the oxidative coupling of various amines to imines, achieving yields of 39–99% within 10–30 min. A key advantage of this system is its reusability; the catalyst maintained remarkable stability and activity over ten reaction cycles with straightforward recovery. This paper-based catalyst offers a promising strategy for eco-friendly and cost-effective synthetic processes, with significant implications for green chemistry and industrial applications.