Recycling of organic ligands and solvents for successive synthesis of Cu-based nanocrystals towards CO2 hydrogenation†

Colloidal synthesis serves as an advanced method for the fabrication of functional Cu-based metal oxide nanocrystals (MO_x NCs) towards CO₂ hydrogenation owing to its capability to finely regulate NCs and its excellent reproducibility, while its practical application is severely hindered by the high cost. The expensive organic ligands of metal precursors and the large volumes of solvents being directly discarded after the fabrication process dominate the cost of colloidal synthesis. Herein, we modified the traditional colloidal synthetic method for the cost-efficient production of high-quality MO_x NCs with the recovery of organic ligands, synthesis solvents, and purification solvents. Furthermore, the recovered solvents were all reused for 5 rounds of successive synthesis of reproducible Cu-based multimetallic oxide NCs. The obtained CuO/ZnO/ZrO₂ NCs were applied to CO₂ hydrogenation and displayed a high formation rate of 413.0 mg_MeOH g_cat.⁻¹ h⁻¹ as well as a selectivity of 77.5% towards methanol over prolonged operations, and were superior to many Cu-based catalysts reported recently.