Reusable magnetic PdxCoy nanoalloys confined in mesoporous carbons for green Suzuki–Miyaura reactions

Abstract

We report herein Pd_xCo_y nanoalloys confined in mesoporous carbons (Pd_x–Co_y@MC) prepared by an eco-friendly one-pot approach consisting in the co-assembly of readily available and non-toxic carbon precursors (phloroglucinol, glyoxal) with a porogen template (pluronic F-127) and metallic salts (H₂PdCl₄ and Co(NO₃)₂·6H₂O) followed by thermal annealing. Three Pd_xCo_y@MC materials with different alloy compositions were prepared (C1: x/y = 90/10; C2: x/y = 75/25; C3 and C4: x/y = 50/50). The nanoalloys were uniformly distributed in the carbon framework and the particle sizes depended on the alloy composition. These composites were then used for Suzuki–Miyaura reactions using either H₂O or a 1 : 1 H₂O/EtOH mixture as solvent. The Pd₅₀Co₅₀@MC catalyst C3 proved to be the most efficient catalyst (in terms of efficiency and magnetic recovery) affording the coupling products in good to excellent yields. After reaction, C3 was recovered quantitatively by simple magnetic separation and reused up to six times without loss of efficiency. The amount of palladium lost in the reaction mixture after magnetic separation was very low (ca. 0.1 % wt of the amount initially used).