Facile synthesis of CoSi alloy catalysts with rich vacancies for base- and solvent-free aerobic oxidation of aromatic alcohols

Abstract

The rational design and green synthesis of low-cost, robust, and efficient catalysts for the selective oxidation of various alcohols are highly challenging. Herein, we report a fast and solvent-free arc-melting (AM) method to controllably synthesize a semimetallic CoSi alloy catalyst (denoted as AM-CoSi) that is efficient in the base- and solvent-free oxidation of six types of aromatic alcohols. X-ray absorption fine structure analysis, electron paramagnetic resonance spectroscopy, and aberration-corrected high angle annular dark field scanning transmission electron microscopy confirmed the successful synthesis of AM-CoSi with abundant Si vacancies (Siv). The as-prepared CoSi alloy catalysts exhibit an order of magnitude greater activity in the oxidation of a model reactant, benzyl alcohol (BAL) to benzyl benzoate (BBE), compared with their mono-counterparts, and provide 70% yield of BBE, the highest yield reported to date. Experimental results and density functional theory calculations suggest that the CoSi alloy structure improves the BAL conversion and that Si vacancy is the main contributor to the generation of BBE, based on which a potential reaction pathway is rationally proposed. Furthermore, the CoSi alloy maintains high stability and also exhibits high activity in the selective oxidation of various alcohols with different functional groups. This work demonstrates for the first time that semimetallic CoSi alloys can be robust catalysts for the green oxidation of various alcohols and proviedes a vast opportunity for the rational design and application of other semimetal alloy catalysts.