Recycling of solvent and reducing agent in metal particle synthesis: proof-of-concept using 2-ethylanthraquinone for copper-based particles

Metallic nano- and micro- materials are relevant for a wide range of applications, from catalysis to medicine. To contribute to the green transition, for more sustainable chemical processes, and to make the most of the unique properties of such materials, it is essential to develop synthesis methods compatible with the principles of Sustainable Science and Technology . In several syntheses, a metal precursor is reduced in a solvent by reducing agents in a liquid phase. However, these reducing agents and solvents are typically sacrificial and/or difficult to recover. Here, we demonstrate a method that follows more closely the principles of Sustainable Chemistry , where the simple reduction of 2-ethylanthraquinone (2-EAQ) by H _2 makes it possible to further mediate the production of metal nanoparticles by reduction of a metal precursor. Conveniently, 2-EAQ is a molecule widely used in the industry for the production of H _2 O _2 and 2-EAQ is easily reduced with hydrogen at room temperature over a commercial nickel catalyst. As an example, the reduced form of 2-EAQ can be used to reduce copper(II)tetrafluoroborate in tetrahydrofuran at room temperature. The effect of the ratios of the chemicals on the size of the resulting materials is investigated. It is found that the acidity of the medium is crucial to tune the selectivity of the reduction to obtain either copper(I)oxide or pure copper material. Solvent and reducing agent can be recovered and regenerated multiple times, paving the way to more sustainable syntheses of metallic particles that generate less waste and avoid the use of sacrificial reducing agents.