Tomasz Baran has got his PhD degree. Congratulation!

Photocatalytic reduction of carbon dioxide in hybrid systems

Carbon dioxide utilization may contribute to controlling its atmosphere level, reducing the emission and recycling carbon. Various methods of CO₂ reduction are under intensive study, including photocatalysis that is promising, environmentally friendly technique of solar to chemical energy conversion. Three strategies of CO₂ reduction to useful chemicals and fuels were investigated: photocatalytic carboxylation of organic compounds with CO₂ reducing coupling, photocatalytic CO₂ reduction to C₁ compounds and bioinspired systems for CO₂ reduction to methanol by an enzymatic way with photocatalytic regeneration of coenzyme. Carboxylation of acetylacetone and 2,3-dihydrofuran with carbon dioxide has been performed by using ZnS-based photocatalysts. The formation of carboxylic acid, as proven by ¹³C NMR, GC-MS and IR, was observed. The reaction efficiency was enhanced after modification of ZnS with ruthenium nanoparticles. The reaction involves one-electron reduction of CO₂ to CO₂^.-with photogenerated electrons from the conduction band of ZnS and one-hole oxidation of organic substrates to the relevant radical. Coupling of formed radicals leads to the formation of carboxylic acids through C-C bound formation. Multielectron CO₂ reduction to C₁ molecules has been studied using various neat and modified materials: ZnS, CuI, NiO, CuS. HCOOH and CO were found as the main reduction products. The amount and ratio of products were influenced by the type of materials, the presence of deposited ruthenium(0) nanoparticles at the surface of materials and solvent polarity. Last approach of CO₂ utilization based on photochemical regeneration of NADH for the enzymatic CO₂ to CH₃OH reduction through the enzymes cascade: F_ateDH, F_aldDH and ADH. A series of photocatalysts was employed as photocatalyst of reduction of NAD⁺ to NADH under visible light irradiation. TiO₂ photosensitized with organic dye and inorganic chromium complexes, narrow band gap photocatalysts such as Cu₂O and InVO₄ as well as ZnS doped with iron or cobalt cations seems to be the most promising photocatalysts. Thorough investigations led to the development of a photocatalytic systems constructed of photocatalyst and electron mediator that yield in selective and efficient regeneration of 1,4-NADH isomer.studied processes can find applications for the solar-light-driven green synthesis of fuels or C_n+1 carboxylic compounds from C_n substrates by utilizing carbon dioxide.