  Rational design and green synthesis of low-cost and robust catalysts
efficient for the selective oxidation of various alcohols are full of
challenges. Herein, we report a fast and solvent-free arc-melting (AM) method
to controllably synthesize semimetal CoSi alloy (abbreviated as AM-CoSi) that
is efficient for the base- and solvent-free oxidation of six types of aromatic
alcohols. X-ray absorption fine structure (XAFS), electron paramagnetic
resonance (EPR), and aberration corrected high angle annular dark field
scanning transmission electron microscope (AC HAADF-STEM) confirmed the
successful synthesis of AM-CoSi with rich Si vacancy (Siv). The as-prepared
CoSi alloy catalysts exhibit an order of magnitude activity enhancement in the
oxidation of model reactant benzyl alcohol (BAL) to benzyl benzoate (BBE)
compared with its mono counterparts, whereas 70 % yield of BBE which is the
highest yield to date. Experimental results and DFT calculations well verify
that the CoSi alloy structure improves the BAL conversion and Si vacancy mainly
contributes to the generation of BBE. After that, CoSi alloy maintains high
stability and a potential pathway is rationally proposed. Besides, CoSi alloy
also efficiently works for the selective oxidation of various alcohols with
different groups. This work demonstrates for the first time that semimetal CoSi
alloy is robust for the green oxidation of various alcohols and provides a vast
opportunity for reasonable design and application of other semimetal alloy
catalysts.
