Currently, there is increased interest in finding environmentally friendly solvents and reducing environmental impact, as well as seeking sustainable and efficient synthesis routes for the production of materials aligned with green chemistry principles for advanced materials. 

Among the solvents of interest are DES (Deep Eutectic Solvents), which have special physicochemical properties such as low toxicity, high efficiency, and the ability to dissolve specific metals, negligible volatility, among others, leading to great potential for applications. 

DES have been used for the extraction of precious metals from electronic waste, in the formulation of drugs and controlled-release systems, among other applications.

On the other hand, tannic acid (TA) is a phenolic compound with antioxidant and antimicrobial properties, among others. It has been used in the blood compatibility of sodium alginate-based materials. Another use of TA is as a stabilizer and structure director in the synthesis of gold nanoparticles.

The research reported in this paper contributes to scientific knowledge in understanding the behavior of TA in the green and sustainable solvent DES formed by ChCl-urea, as well as its main differences with the reported properties of aqueous solutions, in order to find potential applications in the synthesis or processing of nanomaterials in an environmentally friendly medium.