Photodehydration of Ethanol Mediated by CuCl 2 -Ethanol Complex.

Biomass ethanol is regarded as a renewable resource but it is not economically viable to transform it to high-value industrial chemicals at present. Herein, a simple, green, and low-cost CuCl 2 -ethanol complex is reported for ethanol dehydration to produce ethylene and acetal simultaneously with high selectivity under sunlight irradiation. Under N 2 atmosphere, the generation rates of ethylene and acetal were 165 and 3672 μmol g -1 h -1 , accounting for 100% in gas products and 97% in liquid products, respectively. An outstanding apparent quantum yield of 13.2% (365 nm) and the maximum conversion rate of 32% were achieved. The dehydration reactions start from the photoexcited CuCl 2 -ethanol complex, and then go through the energy transfer ( EnT ) and ligand to metal charge transfer ( LMCT ) mechanisms to produce ethylene and acetal, respectively. The formation energies of the CuCl 2 -ethanol complex and the key intermediate radicals (e.g., ·OH, CH 3 CH 2 ·, and CH 3 CH 2 O·) were validated to clarify the mechanisms. Different from previous CuCl 2 -based oxidation and addition reactions, this work is anticipated to supply new insights into the dehydration reaction of ethanol to produce useful chemical feedstocks.