Photocatalytic Carboxylation of Organic Substrates with Carbon Dioxide at Zinc Sulfide with Deposited Ruthenium Nanoparticles

Photocatalytic carboxylation of acetylacetone with carbon dioxide has been performed by using ZnS-based photocatalysts. The formation of two isomeric carboxylic acids, as proven by IR and (CNMR)-C-13 spectroscopy, was observed. The reaction yield was enhanced after deposition of ruthenium nanoparticles on ZnS. The reaction encompasses ruthenium-mediated one-electron reduction of CO2 to CO2.- with electrons from the conduction band of ZnS and one-hole oxidation of acetylacetone to the relevant radical. Coupling of photogenerated radicals leads to the formation of carboxylic acids. Generation of CO2.- has been confirmed by spin-trapping EPR measurements. The process described herein may find applications for the solar-light-driven green synthesis of Cn+1 carboxylic compounds from C-n substrates by utilising carbon dioxide.